1 /* 2 * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.lang; 27 28 import java.math.BigDecimal; 29 import java.util.Random; 30 import jdk.internal.math.FloatConsts; 31 import jdk.internal.math.DoubleConsts; 32 import jdk.internal.HotSpotIntrinsicCandidate; 33 34 /** 35 * The class {@code Math} contains methods for performing basic 36 * numeric operations such as the elementary exponential, logarithm, 37 * square root, and trigonometric functions. 38 * 39 * <p>Unlike some of the numeric methods of class 40 * {@code StrictMath}, all implementations of the equivalent 41 * functions of class {@code Math} are not defined to return the 42 * bit-for-bit same results. This relaxation permits 43 * better-performing implementations where strict reproducibility is 44 * not required. 45 * 46 * <p>By default many of the {@code Math} methods simply call 47 * the equivalent method in {@code StrictMath} for their 48 * implementation. Code generators are encouraged to use 49 * platform-specific native libraries or microprocessor instructions, 50 * where available, to provide higher-performance implementations of 51 * {@code Math} methods. Such higher-performance 52 * implementations still must conform to the specification for 53 * {@code Math}. 54 * 55 * <p>The quality of implementation specifications concern two 56 * properties, accuracy of the returned result and monotonicity of the 57 * method. Accuracy of the floating-point {@code Math} methods is 58 * measured in terms of <i>ulps</i>, units in the last place. For a 59 * given floating-point format, an {@linkplain #ulp(double) ulp} of a 60 * specific real number value is the distance between the two 61 * floating-point values bracketing that numerical value. When 62 * discussing the accuracy of a method as a whole rather than at a 63 * specific argument, the number of ulps cited is for the worst-case 64 * error at any argument. If a method always has an error less than 65 * 0.5 ulps, the method always returns the floating-point number 66 * nearest the exact result; such a method is <i>correctly 67 * rounded</i>. A correctly rounded method is generally the best a 68 * floating-point approximation can be; however, it is impractical for 69 * many floating-point methods to be correctly rounded. Instead, for 70 * the {@code Math} class, a larger error bound of 1 or 2 ulps is 71 * allowed for certain methods. Informally, with a 1 ulp error bound, 72 * when the exact result is a representable number, the exact result 73 * should be returned as the computed result; otherwise, either of the 74 * two floating-point values which bracket the exact result may be 75 * returned. For exact results large in magnitude, one of the 76 * endpoints of the bracket may be infinite. Besides accuracy at 77 * individual arguments, maintaining proper relations between the 78 * method at different arguments is also important. Therefore, most 79 * methods with more than 0.5 ulp errors are required to be 80 * <i>semi-monotonic</i>: whenever the mathematical function is 81 * non-decreasing, so is the floating-point approximation, likewise, 82 * whenever the mathematical function is non-increasing, so is the 83 * floating-point approximation. Not all approximations that have 1 84 * ulp accuracy will automatically meet the monotonicity requirements. 85 * 86 * <p> 87 * The platform uses signed two's complement integer arithmetic with 88 * int and long primitive types. The developer should choose 89 * the primitive type to ensure that arithmetic operations consistently 90 * produce correct results, which in some cases means the operations 91 * will not overflow the range of values of the computation. 92 * The best practice is to choose the primitive type and algorithm to avoid 93 * overflow. In cases where the size is {@code int} or {@code long} and 94 * overflow errors need to be detected, the methods {@code addExact}, 95 * {@code subtractExact}, {@code multiplyExact}, {@code toIntExact}, 96 * {@code incrementExact}, {@code decrementExact} and {@code negateExact} 97 * throw an {@code ArithmeticException} when the results overflow. 98 * For the arithmetic operations divide and absolute value, overflow 99 * occurs only with a specific minimum or maximum value and 100 * should be checked against the minimum or maximum as appropriate. 101 * 102 * @author unascribed 103 * @author Joseph D. Darcy 104 * @since 1.0 105 */ 106 107 public final class Math { 108 109 /** 110 * Don't let anyone instantiate this class. 111 */ 112 private Math() {} 113 114 /** 115 * The {@code double} value that is closer than any other to 116 * <i>e</i>, the base of the natural logarithms. 117 */ 118 public static final double E = 2.7182818284590452354; 119 120 /** 121 * The {@code double} value that is closer than any other to 122 * <i>pi</i>, the ratio of the circumference of a circle to its 123 * diameter. 124 */ 125 public static final double PI = 3.14159265358979323846; 126 127 /** 128 * Constant by which to multiply an angular value in degrees to obtain an 129 * angular value in radians. 130 */ 131 private static final double DEGREES_TO_RADIANS = 0.017453292519943295; 132 133 /** 134 * Constant by which to multiply an angular value in radians to obtain an 135 * angular value in degrees. 136 */ 137 private static final double RADIANS_TO_DEGREES = 57.29577951308232; 138 139 /** 140 * Returns the trigonometric sine of an angle. Special cases: 141 * <ul><li>If the argument is NaN or an infinity, then the 142 * result is NaN. 143 * <li>If the argument is zero, then the result is a zero with the 144 * same sign as the argument.</ul> 145 * 146 * <p>The computed result must be within 1 ulp of the exact result. 147 * Results must be semi-monotonic. 148 * 149 * @param a an angle, in radians. 150 * @return the sine of the argument. 151 */ 152 @HotSpotIntrinsicCandidate 153 public static double sin(double a) { 154 return StrictMath.sin(a); // default impl. delegates to StrictMath 155 } 156 157 /** 158 * Returns the trigonometric cosine of an angle. Special cases: 159 * <ul><li>If the argument is NaN or an infinity, then the 160 * result is NaN.</ul> 161 * 162 * <p>The computed result must be within 1 ulp of the exact result. 163 * Results must be semi-monotonic. 164 * 165 * @param a an angle, in radians. 166 * @return the cosine of the argument. 167 */ 168 @HotSpotIntrinsicCandidate 169 public static double cos(double a) { 170 return StrictMath.cos(a); // default impl. delegates to StrictMath 171 } 172 173 /** 174 * Returns the trigonometric tangent of an angle. Special cases: 175 * <ul><li>If the argument is NaN or an infinity, then the result 176 * is NaN. 177 * <li>If the argument is zero, then the result is a zero with the 178 * same sign as the argument.</ul> 179 * 180 * <p>The computed result must be within 1 ulp of the exact result. 181 * Results must be semi-monotonic. 182 * 183 * @param a an angle, in radians. 184 * @return the tangent of the argument. 185 */ 186 @HotSpotIntrinsicCandidate 187 public static double tan(double a) { 188 return StrictMath.tan(a); // default impl. delegates to StrictMath 189 } 190 191 /** 192 * Returns the arc sine of a value; the returned angle is in the 193 * range -<i>pi</i>/2 through <i>pi</i>/2. Special cases: 194 * <ul><li>If the argument is NaN or its absolute value is greater 195 * than 1, then the result is NaN. 196 * <li>If the argument is zero, then the result is a zero with the 197 * same sign as the argument.</ul> 198 * 199 * <p>The computed result must be within 1 ulp of the exact result. 200 * Results must be semi-monotonic. 201 * 202 * @param a the value whose arc sine is to be returned. 203 * @return the arc sine of the argument. 204 */ 205 public static double asin(double a) { 206 return StrictMath.asin(a); // default impl. delegates to StrictMath 207 } 208 209 /** 210 * Returns the arc cosine of a value; the returned angle is in the 211 * range 0.0 through <i>pi</i>. Special case: 212 * <ul><li>If the argument is NaN or its absolute value is greater 213 * than 1, then the result is NaN.</ul> 214 * 215 * <p>The computed result must be within 1 ulp of the exact result. 216 * Results must be semi-monotonic. 217 * 218 * @param a the value whose arc cosine is to be returned. 219 * @return the arc cosine of the argument. 220 */ 221 public static double acos(double a) { 222 return StrictMath.acos(a); // default impl. delegates to StrictMath 223 } 224 225 /** 226 * Returns the arc tangent of a value; the returned angle is in the 227 * range -<i>pi</i>/2 through <i>pi</i>/2. Special cases: 228 * <ul><li>If the argument is NaN, then the result is NaN. 229 * <li>If the argument is zero, then the result is a zero with the 230 * same sign as the argument.</ul> 231 * 232 * <p>The computed result must be within 1 ulp of the exact result. 233 * Results must be semi-monotonic. 234 * 235 * @param a the value whose arc tangent is to be returned. 236 * @return the arc tangent of the argument. 237 */ 238 public static double atan(double a) { 239 return StrictMath.atan(a); // default impl. delegates to StrictMath 240 } 241 242 /** 243 * Converts an angle measured in degrees to an approximately 244 * equivalent angle measured in radians. The conversion from 245 * degrees to radians is generally inexact. 246 * 247 * @param angdeg an angle, in degrees 248 * @return the measurement of the angle {@code angdeg} 249 * in radians. 250 * @since 1.2 251 */ 252 public static double toRadians(double angdeg) { 253 return angdeg * DEGREES_TO_RADIANS; 254 } 255 256 /** 257 * Converts an angle measured in radians to an approximately 258 * equivalent angle measured in degrees. The conversion from 259 * radians to degrees is generally inexact; users should 260 * <i>not</i> expect {@code cos(toRadians(90.0))} to exactly 261 * equal {@code 0.0}. 262 * 263 * @param angrad an angle, in radians 264 * @return the measurement of the angle {@code angrad} 265 * in degrees. 266 * @since 1.2 267 */ 268 public static double toDegrees(double angrad) { 269 return angrad * RADIANS_TO_DEGREES; 270 } 271 272 /** 273 * Returns Euler's number <i>e</i> raised to the power of a 274 * {@code double} value. Special cases: 275 * <ul><li>If the argument is NaN, the result is NaN. 276 * <li>If the argument is positive infinity, then the result is 277 * positive infinity. 278 * <li>If the argument is negative infinity, then the result is 279 * positive zero.</ul> 280 * 281 * <p>The computed result must be within 1 ulp of the exact result. 282 * Results must be semi-monotonic. 283 * 284 * @param a the exponent to raise <i>e</i> to. 285 * @return the value <i>e</i><sup>{@code a}</sup>, 286 * where <i>e</i> is the base of the natural logarithms. 287 */ 288 @HotSpotIntrinsicCandidate 289 public static double exp(double a) { 290 return StrictMath.exp(a); // default impl. delegates to StrictMath 291 } 292 293 /** 294 * Returns the natural logarithm (base <i>e</i>) of a {@code double} 295 * value. Special cases: 296 * <ul><li>If the argument is NaN or less than zero, then the result 297 * is NaN. 298 * <li>If the argument is positive infinity, then the result is 299 * positive infinity. 300 * <li>If the argument is positive zero or negative zero, then the 301 * result is negative infinity.</ul> 302 * 303 * <p>The computed result must be within 1 ulp of the exact result. 304 * Results must be semi-monotonic. 305 * 306 * @param a a value 307 * @return the value ln {@code a}, the natural logarithm of 308 * {@code a}. 309 */ 310 @HotSpotIntrinsicCandidate 311 public static double log(double a) { 312 return StrictMath.log(a); // default impl. delegates to StrictMath 313 } 314 315 /** 316 * Returns the base 10 logarithm of a {@code double} value. 317 * Special cases: 318 * 319 * <ul><li>If the argument is NaN or less than zero, then the result 320 * is NaN. 321 * <li>If the argument is positive infinity, then the result is 322 * positive infinity. 323 * <li>If the argument is positive zero or negative zero, then the 324 * result is negative infinity. 325 * <li> If the argument is equal to 10<sup><i>n</i></sup> for 326 * integer <i>n</i>, then the result is <i>n</i>. 327 * </ul> 328 * 329 * <p>The computed result must be within 1 ulp of the exact result. 330 * Results must be semi-monotonic. 331 * 332 * @param a a value 333 * @return the base 10 logarithm of {@code a}. 334 * @since 1.5 335 */ 336 @HotSpotIntrinsicCandidate 337 public static double log10(double a) { 338 return StrictMath.log10(a); // default impl. delegates to StrictMath 339 } 340 341 /** 342 * Returns the correctly rounded positive square root of a 343 * {@code double} value. 344 * Special cases: 345 * <ul><li>If the argument is NaN or less than zero, then the result 346 * is NaN. 347 * <li>If the argument is positive infinity, then the result is positive 348 * infinity. 349 * <li>If the argument is positive zero or negative zero, then the 350 * result is the same as the argument.</ul> 351 * Otherwise, the result is the {@code double} value closest to 352 * the true mathematical square root of the argument value. 353 * 354 * @param a a value. 355 * @return the positive square root of {@code a}. 356 * If the argument is NaN or less than zero, the result is NaN. 357 */ 358 @HotSpotIntrinsicCandidate 359 public static double sqrt(double a) { 360 return StrictMath.sqrt(a); // default impl. delegates to StrictMath 361 // Note that hardware sqrt instructions 362 // frequently can be directly used by JITs 363 // and should be much faster than doing 364 // Math.sqrt in software. 365 } 366 367 368 /** 369 * Returns the cube root of a {@code double} value. For 370 * positive finite {@code x}, {@code cbrt(-x) == 371 * -cbrt(x)}; that is, the cube root of a negative value is 372 * the negative of the cube root of that value's magnitude. 373 * 374 * Special cases: 375 * 376 * <ul> 377 * 378 * <li>If the argument is NaN, then the result is NaN. 379 * 380 * <li>If the argument is infinite, then the result is an infinity 381 * with the same sign as the argument. 382 * 383 * <li>If the argument is zero, then the result is a zero with the 384 * same sign as the argument. 385 * 386 * </ul> 387 * 388 * <p>The computed result must be within 1 ulp of the exact result. 389 * 390 * @param a a value. 391 * @return the cube root of {@code a}. 392 * @since 1.5 393 */ 394 public static double cbrt(double a) { 395 return StrictMath.cbrt(a); 396 } 397 398 /** 399 * Computes the remainder operation on two arguments as prescribed 400 * by the IEEE 754 standard. 401 * The remainder value is mathematically equal to 402 * <code>f1 - f2</code> × <i>n</i>, 403 * where <i>n</i> is the mathematical integer closest to the exact 404 * mathematical value of the quotient {@code f1/f2}, and if two 405 * mathematical integers are equally close to {@code f1/f2}, 406 * then <i>n</i> is the integer that is even. If the remainder is 407 * zero, its sign is the same as the sign of the first argument. 408 * Special cases: 409 * <ul><li>If either argument is NaN, or the first argument is infinite, 410 * or the second argument is positive zero or negative zero, then the 411 * result is NaN. 412 * <li>If the first argument is finite and the second argument is 413 * infinite, then the result is the same as the first argument.</ul> 414 * 415 * @param f1 the dividend. 416 * @param f2 the divisor. 417 * @return the remainder when {@code f1} is divided by 418 * {@code f2}. 419 */ 420 public static double IEEEremainder(double f1, double f2) { 421 return StrictMath.IEEEremainder(f1, f2); // delegate to StrictMath 422 } 423 424 /** 425 * Returns the smallest (closest to negative infinity) 426 * {@code double} value that is greater than or equal to the 427 * argument and is equal to a mathematical integer. Special cases: 428 * <ul><li>If the argument value is already equal to a 429 * mathematical integer, then the result is the same as the 430 * argument. <li>If the argument is NaN or an infinity or 431 * positive zero or negative zero, then the result is the same as 432 * the argument. <li>If the argument value is less than zero but 433 * greater than -1.0, then the result is negative zero.</ul> Note 434 * that the value of {@code Math.ceil(x)} is exactly the 435 * value of {@code -Math.floor(-x)}. 436 * 437 * 438 * @param a a value. 439 * @return the smallest (closest to negative infinity) 440 * floating-point value that is greater than or equal to 441 * the argument and is equal to a mathematical integer. 442 */ 443 @HotSpotIntrinsicCandidate 444 public static double ceil(double a) { 445 return StrictMath.ceil(a); // default impl. delegates to StrictMath 446 } 447 448 /** 449 * Returns the largest (closest to positive infinity) 450 * {@code double} value that is less than or equal to the 451 * argument and is equal to a mathematical integer. Special cases: 452 * <ul><li>If the argument value is already equal to a 453 * mathematical integer, then the result is the same as the 454 * argument. <li>If the argument is NaN or an infinity or 455 * positive zero or negative zero, then the result is the same as 456 * the argument.</ul> 457 * 458 * @param a a value. 459 * @return the largest (closest to positive infinity) 460 * floating-point value that less than or equal to the argument 461 * and is equal to a mathematical integer. 462 */ 463 @HotSpotIntrinsicCandidate 464 public static double floor(double a) { 465 return StrictMath.floor(a); // default impl. delegates to StrictMath 466 } 467 468 /** 469 * Returns the {@code double} value that is closest in value 470 * to the argument and is equal to a mathematical integer. If two 471 * {@code double} values that are mathematical integers are 472 * equally close, the result is the integer value that is 473 * even. Special cases: 474 * <ul><li>If the argument value is already equal to a mathematical 475 * integer, then the result is the same as the argument. 476 * <li>If the argument is NaN or an infinity or positive zero or negative 477 * zero, then the result is the same as the argument.</ul> 478 * 479 * @param a a {@code double} value. 480 * @return the closest floating-point value to {@code a} that is 481 * equal to a mathematical integer. 482 */ 483 @HotSpotIntrinsicCandidate 484 public static double rint(double a) { 485 return StrictMath.rint(a); // default impl. delegates to StrictMath 486 } 487 488 /** 489 * Returns the angle <i>theta</i> from the conversion of rectangular 490 * coordinates ({@code x}, {@code y}) to polar 491 * coordinates (r, <i>theta</i>). 492 * This method computes the phase <i>theta</i> by computing an arc tangent 493 * of {@code y/x} in the range of -<i>pi</i> to <i>pi</i>. Special 494 * cases: 495 * <ul><li>If either argument is NaN, then the result is NaN. 496 * <li>If the first argument is positive zero and the second argument 497 * is positive, or the first argument is positive and finite and the 498 * second argument is positive infinity, then the result is positive 499 * zero. 500 * <li>If the first argument is negative zero and the second argument 501 * is positive, or the first argument is negative and finite and the 502 * second argument is positive infinity, then the result is negative zero. 503 * <li>If the first argument is positive zero and the second argument 504 * is negative, or the first argument is positive and finite and the 505 * second argument is negative infinity, then the result is the 506 * {@code double} value closest to <i>pi</i>. 507 * <li>If the first argument is negative zero and the second argument 508 * is negative, or the first argument is negative and finite and the 509 * second argument is negative infinity, then the result is the 510 * {@code double} value closest to -<i>pi</i>. 511 * <li>If the first argument is positive and the second argument is 512 * positive zero or negative zero, or the first argument is positive 513 * infinity and the second argument is finite, then the result is the 514 * {@code double} value closest to <i>pi</i>/2. 515 * <li>If the first argument is negative and the second argument is 516 * positive zero or negative zero, or the first argument is negative 517 * infinity and the second argument is finite, then the result is the 518 * {@code double} value closest to -<i>pi</i>/2. 519 * <li>If both arguments are positive infinity, then the result is the 520 * {@code double} value closest to <i>pi</i>/4. 521 * <li>If the first argument is positive infinity and the second argument 522 * is negative infinity, then the result is the {@code double} 523 * value closest to 3*<i>pi</i>/4. 524 * <li>If the first argument is negative infinity and the second argument 525 * is positive infinity, then the result is the {@code double} value 526 * closest to -<i>pi</i>/4. 527 * <li>If both arguments are negative infinity, then the result is the 528 * {@code double} value closest to -3*<i>pi</i>/4.</ul> 529 * 530 * <p>The computed result must be within 2 ulps of the exact result. 531 * Results must be semi-monotonic. 532 * 533 * @param y the ordinate coordinate 534 * @param x the abscissa coordinate 535 * @return the <i>theta</i> component of the point 536 * (<i>r</i>, <i>theta</i>) 537 * in polar coordinates that corresponds to the point 538 * (<i>x</i>, <i>y</i>) in Cartesian coordinates. 539 */ 540 @HotSpotIntrinsicCandidate 541 public static double atan2(double y, double x) { 542 return StrictMath.atan2(y, x); // default impl. delegates to StrictMath 543 } 544 545 /** 546 * Returns the value of the first argument raised to the power of the 547 * second argument. Special cases: 548 * 549 * <ul><li>If the second argument is positive or negative zero, then the 550 * result is 1.0. 551 * <li>If the second argument is 1.0, then the result is the same as the 552 * first argument. 553 * <li>If the second argument is NaN, then the result is NaN. 554 * <li>If the first argument is NaN and the second argument is nonzero, 555 * then the result is NaN. 556 * 557 * <li>If 558 * <ul> 559 * <li>the absolute value of the first argument is greater than 1 560 * and the second argument is positive infinity, or 561 * <li>the absolute value of the first argument is less than 1 and 562 * the second argument is negative infinity, 563 * </ul> 564 * then the result is positive infinity. 565 * 566 * <li>If 567 * <ul> 568 * <li>the absolute value of the first argument is greater than 1 and 569 * the second argument is negative infinity, or 570 * <li>the absolute value of the 571 * first argument is less than 1 and the second argument is positive 572 * infinity, 573 * </ul> 574 * then the result is positive zero. 575 * 576 * <li>If the absolute value of the first argument equals 1 and the 577 * second argument is infinite, then the result is NaN. 578 * 579 * <li>If 580 * <ul> 581 * <li>the first argument is positive zero and the second argument 582 * is greater than zero, or 583 * <li>the first argument is positive infinity and the second 584 * argument is less than zero, 585 * </ul> 586 * then the result is positive zero. 587 * 588 * <li>If 589 * <ul> 590 * <li>the first argument is positive zero and the second argument 591 * is less than zero, or 592 * <li>the first argument is positive infinity and the second 593 * argument is greater than zero, 594 * </ul> 595 * then the result is positive infinity. 596 * 597 * <li>If 598 * <ul> 599 * <li>the first argument is negative zero and the second argument 600 * is greater than zero but not a finite odd integer, or 601 * <li>the first argument is negative infinity and the second 602 * argument is less than zero but not a finite odd integer, 603 * </ul> 604 * then the result is positive zero. 605 * 606 * <li>If 607 * <ul> 608 * <li>the first argument is negative zero and the second argument 609 * is a positive finite odd integer, or 610 * <li>the first argument is negative infinity and the second 611 * argument is a negative finite odd integer, 612 * </ul> 613 * then the result is negative zero. 614 * 615 * <li>If 616 * <ul> 617 * <li>the first argument is negative zero and the second argument 618 * is less than zero but not a finite odd integer, or 619 * <li>the first argument is negative infinity and the second 620 * argument is greater than zero but not a finite odd integer, 621 * </ul> 622 * then the result is positive infinity. 623 * 624 * <li>If 625 * <ul> 626 * <li>the first argument is negative zero and the second argument 627 * is a negative finite odd integer, or 628 * <li>the first argument is negative infinity and the second 629 * argument is a positive finite odd integer, 630 * </ul> 631 * then the result is negative infinity. 632 * 633 * <li>If the first argument is finite and less than zero 634 * <ul> 635 * <li> if the second argument is a finite even integer, the 636 * result is equal to the result of raising the absolute value of 637 * the first argument to the power of the second argument 638 * 639 * <li>if the second argument is a finite odd integer, the result 640 * is equal to the negative of the result of raising the absolute 641 * value of the first argument to the power of the second 642 * argument 643 * 644 * <li>if the second argument is finite and not an integer, then 645 * the result is NaN. 646 * </ul> 647 * 648 * <li>If both arguments are integers, then the result is exactly equal 649 * to the mathematical result of raising the first argument to the power 650 * of the second argument if that result can in fact be represented 651 * exactly as a {@code double} value.</ul> 652 * 653 * <p>(In the foregoing descriptions, a floating-point value is 654 * considered to be an integer if and only if it is finite and a 655 * fixed point of the method {@link #ceil ceil} or, 656 * equivalently, a fixed point of the method {@link #floor 657 * floor}. A value is a fixed point of a one-argument 658 * method if and only if the result of applying the method to the 659 * value is equal to the value.) 660 * 661 * <p>The computed result must be within 1 ulp of the exact result. 662 * Results must be semi-monotonic. 663 * 664 * @param a the base. 665 * @param b the exponent. 666 * @return the value {@code a}<sup>{@code b}</sup>. 667 */ 668 @HotSpotIntrinsicCandidate 669 public static double pow(double a, double b) { 670 return StrictMath.pow(a, b); // default impl. delegates to StrictMath 671 } 672 673 /** 674 * Returns the closest {@code int} to the argument, with ties 675 * rounding to positive infinity. 676 * 677 * <p> 678 * Special cases: 679 * <ul><li>If the argument is NaN, the result is 0. 680 * <li>If the argument is negative infinity or any value less than or 681 * equal to the value of {@code Integer.MIN_VALUE}, the result is 682 * equal to the value of {@code Integer.MIN_VALUE}. 683 * <li>If the argument is positive infinity or any value greater than or 684 * equal to the value of {@code Integer.MAX_VALUE}, the result is 685 * equal to the value of {@code Integer.MAX_VALUE}.</ul> 686 * 687 * @param a a floating-point value to be rounded to an integer. 688 * @return the value of the argument rounded to the nearest 689 * {@code int} value. 690 * @see java.lang.Integer#MAX_VALUE 691 * @see java.lang.Integer#MIN_VALUE 692 */ 693 public static int round(float a) { 694 int intBits = Float.floatToRawIntBits(a); 695 int biasedExp = (intBits & FloatConsts.EXP_BIT_MASK) 696 >> (FloatConsts.SIGNIFICAND_WIDTH - 1); 697 int shift = (FloatConsts.SIGNIFICAND_WIDTH - 2 698 + FloatConsts.EXP_BIAS) - biasedExp; 699 if ((shift & -32) == 0) { // shift >= 0 && shift < 32 700 // a is a finite number such that pow(2,-32) <= ulp(a) < 1 701 int r = ((intBits & FloatConsts.SIGNIF_BIT_MASK) 702 | (FloatConsts.SIGNIF_BIT_MASK + 1)); 703 if (intBits < 0) { 704 r = -r; 705 } 706 // In the comments below each Java expression evaluates to the value 707 // the corresponding mathematical expression: 708 // (r) evaluates to a / ulp(a) 709 // (r >> shift) evaluates to floor(a * 2) 710 // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2) 711 // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2) 712 return ((r >> shift) + 1) >> 1; 713 } else { 714 // a is either 715 // - a finite number with abs(a) < exp(2,FloatConsts.SIGNIFICAND_WIDTH-32) < 1/2 716 // - a finite number with ulp(a) >= 1 and hence a is a mathematical integer 717 // - an infinity or NaN 718 return (int) a; 719 } 720 } 721 722 /** 723 * Returns the closest {@code long} to the argument, with ties 724 * rounding to positive infinity. 725 * 726 * <p>Special cases: 727 * <ul><li>If the argument is NaN, the result is 0. 728 * <li>If the argument is negative infinity or any value less than or 729 * equal to the value of {@code Long.MIN_VALUE}, the result is 730 * equal to the value of {@code Long.MIN_VALUE}. 731 * <li>If the argument is positive infinity or any value greater than or 732 * equal to the value of {@code Long.MAX_VALUE}, the result is 733 * equal to the value of {@code Long.MAX_VALUE}.</ul> 734 * 735 * @param a a floating-point value to be rounded to a 736 * {@code long}. 737 * @return the value of the argument rounded to the nearest 738 * {@code long} value. 739 * @see java.lang.Long#MAX_VALUE 740 * @see java.lang.Long#MIN_VALUE 741 */ 742 public static long round(double a) { 743 long longBits = Double.doubleToRawLongBits(a); 744 long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK) 745 >> (DoubleConsts.SIGNIFICAND_WIDTH - 1); 746 long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2 747 + DoubleConsts.EXP_BIAS) - biasedExp; 748 if ((shift & -64) == 0) { // shift >= 0 && shift < 64 749 // a is a finite number such that pow(2,-64) <= ulp(a) < 1 750 long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK) 751 | (DoubleConsts.SIGNIF_BIT_MASK + 1)); 752 if (longBits < 0) { 753 r = -r; 754 } 755 // In the comments below each Java expression evaluates to the value 756 // the corresponding mathematical expression: 757 // (r) evaluates to a / ulp(a) 758 // (r >> shift) evaluates to floor(a * 2) 759 // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2) 760 // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2) 761 return ((r >> shift) + 1) >> 1; 762 } else { 763 // a is either 764 // - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2 765 // - a finite number with ulp(a) >= 1 and hence a is a mathematical integer 766 // - an infinity or NaN 767 return (long) a; 768 } 769 } 770 771 private static final class RandomNumberGeneratorHolder { 772 static final Random randomNumberGenerator = new Random(); 773 } 774 775 /** 776 * Returns a {@code double} value with a positive sign, greater 777 * than or equal to {@code 0.0} and less than {@code 1.0}. 778 * Returned values are chosen pseudorandomly with (approximately) 779 * uniform distribution from that range. 780 * 781 * <p>When this method is first called, it creates a single new 782 * pseudorandom-number generator, exactly as if by the expression 783 * 784 * <blockquote>{@code new java.util.Random()}</blockquote> 785 * 786 * This new pseudorandom-number generator is used thereafter for 787 * all calls to this method and is used nowhere else. 788 * 789 * <p>This method is properly synchronized to allow correct use by 790 * more than one thread. However, if many threads need to generate 791 * pseudorandom numbers at a great rate, it may reduce contention 792 * for each thread to have its own pseudorandom-number generator. 793 * 794 * @apiNote 795 * As the largest {@code double} value less than {@code 1.0} 796 * is {@code Math.nextDown(1.0)}, a value {@code x} in the closed range 797 * {@code [x1,x2]} where {@code x1<=x2} may be defined by the statements 798 * 799 * <blockquote><pre>{@code 800 * double f = Math.random()/Math.nextDown(1.0); 801 * double x = x1*(1.0 - f) + x2*f; 802 * }</pre></blockquote> 803 * 804 * @return a pseudorandom {@code double} greater than or equal 805 * to {@code 0.0} and less than {@code 1.0}. 806 * @see #nextDown(double) 807 * @see Random#nextDouble() 808 */ 809 public static double random() { 810 return RandomNumberGeneratorHolder.randomNumberGenerator.nextDouble(); 811 } 812 813 /** 814 * Returns the sum of its arguments, 815 * throwing an exception if the result overflows an {@code int}. 816 * 817 * @param x the first value 818 * @param y the second value 819 * @return the result 820 * @throws ArithmeticException if the result overflows an int 821 * @since 1.8 822 */ 823 @HotSpotIntrinsicCandidate 824 public static int addExact(int x, int y) { 825 int r = x + y; 826 // HD 2-12 Overflow iff both arguments have the opposite sign of the result 827 if (((x ^ r) & (y ^ r)) < 0) { 828 throw new ArithmeticException("integer overflow"); 829 } 830 return r; 831 } 832 833 /** 834 * Returns the sum of its arguments, 835 * throwing an exception if the result overflows a {@code long}. 836 * 837 * @param x the first value 838 * @param y the second value 839 * @return the result 840 * @throws ArithmeticException if the result overflows a long 841 * @since 1.8 842 */ 843 @HotSpotIntrinsicCandidate 844 public static long addExact(long x, long y) { 845 long r = x + y; 846 // HD 2-12 Overflow iff both arguments have the opposite sign of the result 847 if (((x ^ r) & (y ^ r)) < 0) { 848 throw new ArithmeticException("long overflow"); 849 } 850 return r; 851 } 852 853 /** 854 * Returns the difference of the arguments, 855 * throwing an exception if the result overflows an {@code int}. 856 * 857 * @param x the first value 858 * @param y the second value to subtract from the first 859 * @return the result 860 * @throws ArithmeticException if the result overflows an int 861 * @since 1.8 862 */ 863 @HotSpotIntrinsicCandidate 864 public static int subtractExact(int x, int y) { 865 int r = x - y; 866 // HD 2-12 Overflow iff the arguments have different signs and 867 // the sign of the result is different from the sign of x 868 if (((x ^ y) & (x ^ r)) < 0) { 869 throw new ArithmeticException("integer overflow"); 870 } 871 return r; 872 } 873 874 /** 875 * Returns the difference of the arguments, 876 * throwing an exception if the result overflows a {@code long}. 877 * 878 * @param x the first value 879 * @param y the second value to subtract from the first 880 * @return the result 881 * @throws ArithmeticException if the result overflows a long 882 * @since 1.8 883 */ 884 @HotSpotIntrinsicCandidate 885 public static long subtractExact(long x, long y) { 886 long r = x - y; 887 // HD 2-12 Overflow iff the arguments have different signs and 888 // the sign of the result is different from the sign of x 889 if (((x ^ y) & (x ^ r)) < 0) { 890 throw new ArithmeticException("long overflow"); 891 } 892 return r; 893 } 894 895 /** 896 * Returns the product of the arguments, 897 * throwing an exception if the result overflows an {@code int}. 898 * 899 * @param x the first value 900 * @param y the second value 901 * @return the result 902 * @throws ArithmeticException if the result overflows an int 903 * @since 1.8 904 */ 905 @HotSpotIntrinsicCandidate 906 public static int multiplyExact(int x, int y) { 907 long r = (long)x * (long)y; 908 if ((int)r != r) { 909 throw new ArithmeticException("integer overflow"); 910 } 911 return (int)r; 912 } 913 914 /** 915 * Returns the product of the arguments, throwing an exception if the result 916 * overflows a {@code long}. 917 * 918 * @param x the first value 919 * @param y the second value 920 * @return the result 921 * @throws ArithmeticException if the result overflows a long 922 * @since 9 923 */ 924 public static long multiplyExact(long x, int y) { 925 return multiplyExact(x, (long)y); 926 } 927 928 /** 929 * Returns the product of the arguments, 930 * throwing an exception if the result overflows a {@code long}. 931 * 932 * @param x the first value 933 * @param y the second value 934 * @return the result 935 * @throws ArithmeticException if the result overflows a long 936 * @since 1.8 937 */ 938 @HotSpotIntrinsicCandidate 939 public static long multiplyExact(long x, long y) { 940 long r = x * y; 941 long ax = Math.abs(x); 942 long ay = Math.abs(y); 943 if (((ax | ay) >>> 31 != 0)) { 944 // Some bits greater than 2^31 that might cause overflow 945 // Check the result using the divide operator 946 // and check for the special case of Long.MIN_VALUE * -1 947 if (((y != 0) && (r / y != x)) || 948 (x == Long.MIN_VALUE && y == -1)) { 949 throw new ArithmeticException("long overflow"); 950 } 951 } 952 return r; 953 } 954 955 /** 956 * Returns the argument incremented by one, throwing an exception if the 957 * result overflows an {@code int}. 958 * The overflow only occurs for {@linkplain Integer#MAX_VALUE the maximum value}. 959 * 960 * @param a the value to increment 961 * @return the result 962 * @throws ArithmeticException if the result overflows an int 963 * @since 1.8 964 */ 965 @HotSpotIntrinsicCandidate 966 public static int incrementExact(int a) { 967 if (a == Integer.MAX_VALUE) { 968 throw new ArithmeticException("integer overflow"); 969 } 970 971 return a + 1; 972 } 973 974 /** 975 * Returns the argument incremented by one, throwing an exception if the 976 * result overflows a {@code long}. 977 * The overflow only occurs for {@linkplain Long#MAX_VALUE the maximum value}. 978 * 979 * @param a the value to increment 980 * @return the result 981 * @throws ArithmeticException if the result overflows a long 982 * @since 1.8 983 */ 984 @HotSpotIntrinsicCandidate 985 public static long incrementExact(long a) { 986 if (a == Long.MAX_VALUE) { 987 throw new ArithmeticException("long overflow"); 988 } 989 990 return a + 1L; 991 } 992 993 /** 994 * Returns the argument decremented by one, throwing an exception if the 995 * result overflows an {@code int}. 996 * The overflow only occurs for {@linkplain Integer#MIN_VALUE the minimum value}. 997 * 998 * @param a the value to decrement 999 * @return the result 1000 * @throws ArithmeticException if the result overflows an int 1001 * @since 1.8 1002 */ 1003 @HotSpotIntrinsicCandidate 1004 public static int decrementExact(int a) { 1005 if (a == Integer.MIN_VALUE) { 1006 throw new ArithmeticException("integer overflow"); 1007 } 1008 1009 return a - 1; 1010 } 1011 1012 /** 1013 * Returns the argument decremented by one, throwing an exception if the 1014 * result overflows a {@code long}. 1015 * The overflow only occurs for {@linkplain Long#MIN_VALUE the minimum value}. 1016 * 1017 * @param a the value to decrement 1018 * @return the result 1019 * @throws ArithmeticException if the result overflows a long 1020 * @since 1.8 1021 */ 1022 @HotSpotIntrinsicCandidate 1023 public static long decrementExact(long a) { 1024 if (a == Long.MIN_VALUE) { 1025 throw new ArithmeticException("long overflow"); 1026 } 1027 1028 return a - 1L; 1029 } 1030 1031 /** 1032 * Returns the negation of the argument, throwing an exception if the 1033 * result overflows an {@code int}. 1034 * The overflow only occurs for {@linkplain Integer#MIN_VALUE the minimum value}. 1035 * 1036 * @param a the value to negate 1037 * @return the result 1038 * @throws ArithmeticException if the result overflows an int 1039 * @since 1.8 1040 */ 1041 @HotSpotIntrinsicCandidate 1042 public static int negateExact(int a) { 1043 if (a == Integer.MIN_VALUE) { 1044 throw new ArithmeticException("integer overflow"); 1045 } 1046 1047 return -a; 1048 } 1049 1050 /** 1051 * Returns the negation of the argument, throwing an exception if the 1052 * result overflows a {@code long}. 1053 * The overflow only occurs for {@linkplain Long#MIN_VALUE the minimum value}. 1054 * 1055 * @param a the value to negate 1056 * @return the result 1057 * @throws ArithmeticException if the result overflows a long 1058 * @since 1.8 1059 */ 1060 @HotSpotIntrinsicCandidate 1061 public static long negateExact(long a) { 1062 if (a == Long.MIN_VALUE) { 1063 throw new ArithmeticException("long overflow"); 1064 } 1065 1066 return -a; 1067 } 1068 1069 /** 1070 * Returns the value of the {@code long} argument, 1071 * throwing an exception if the value overflows an {@code int}. 1072 * 1073 * @param value the long value 1074 * @return the argument as an int 1075 * @throws ArithmeticException if the {@code argument} overflows an int 1076 * @since 1.8 1077 */ 1078 public static int toIntExact(long value) { 1079 if ((int)value != value) { 1080 throw new ArithmeticException("integer overflow"); 1081 } 1082 return (int)value; 1083 } 1084 1085 /** 1086 * Returns the exact mathematical product of the arguments. 1087 * 1088 * @param x the first value 1089 * @param y the second value 1090 * @return the result 1091 * @since 9 1092 */ 1093 public static long multiplyFull(int x, int y) { 1094 return (long)x * (long)y; 1095 } 1096 1097 /** 1098 * Returns as a {@code long} the most significant 64 bits of the 128-bit 1099 * product of two 64-bit factors. 1100 * 1101 * @param x the first value 1102 * @param y the second value 1103 * @return the result 1104 * @since 9 1105 */ 1106 @HotSpotIntrinsicCandidate 1107 public static long multiplyHigh(long x, long y) { 1108 if (x < 0 || y < 0) { 1109 // Use technique from section 8-2 of Henry S. Warren, Jr., 1110 // Hacker's Delight (2nd ed.) (Addison Wesley, 2013), 173-174. 1111 long x1 = x >> 32; 1112 long x2 = x & 0xFFFFFFFFL; 1113 long y1 = y >> 32; 1114 long y2 = y & 0xFFFFFFFFL; 1115 long z2 = x2 * y2; 1116 long t = x1 * y2 + (z2 >>> 32); 1117 long z1 = t & 0xFFFFFFFFL; 1118 long z0 = t >> 32; 1119 z1 += x2 * y1; 1120 return x1 * y1 + z0 + (z1 >> 32); 1121 } else { 1122 // Use Karatsuba technique with two base 2^32 digits. 1123 long x1 = x >>> 32; 1124 long y1 = y >>> 32; 1125 long x2 = x & 0xFFFFFFFFL; 1126 long y2 = y & 0xFFFFFFFFL; 1127 long A = x1 * y1; 1128 long B = x2 * y2; 1129 long C = (x1 + x2) * (y1 + y2); 1130 long K = C - A - B; 1131 return (((B >>> 32) + K) >>> 32) + A; 1132 } 1133 } 1134 1135 /** 1136 * Returns the largest (closest to positive infinity) 1137 * {@code int} value that is less than or equal to the algebraic quotient. 1138 * There is one special case, if the dividend is the 1139 * {@linkplain Integer#MIN_VALUE Integer.MIN_VALUE} and the divisor is {@code -1}, 1140 * then integer overflow occurs and 1141 * the result is equal to {@code Integer.MIN_VALUE}. 1142 * <p> 1143 * Normal integer division operates under the round to zero rounding mode 1144 * (truncation). This operation instead acts under the round toward 1145 * negative infinity (floor) rounding mode. 1146 * The floor rounding mode gives different results from truncation 1147 * when the exact result is negative. 1148 * <ul> 1149 * <li>If the signs of the arguments are the same, the results of 1150 * {@code floorDiv} and the {@code /} operator are the same. <br> 1151 * For example, {@code floorDiv(4, 3) == 1} and {@code (4 / 3) == 1}.</li> 1152 * <li>If the signs of the arguments are different, the quotient is negative and 1153 * {@code floorDiv} returns the integer less than or equal to the quotient 1154 * and the {@code /} operator returns the integer closest to zero.<br> 1155 * For example, {@code floorDiv(-4, 3) == -2}, 1156 * whereas {@code (-4 / 3) == -1}. 1157 * </li> 1158 * </ul> 1159 * 1160 * @param x the dividend 1161 * @param y the divisor 1162 * @return the largest (closest to positive infinity) 1163 * {@code int} value that is less than or equal to the algebraic quotient. 1164 * @throws ArithmeticException if the divisor {@code y} is zero 1165 * @see #floorMod(int, int) 1166 * @see #floor(double) 1167 * @since 1.8 1168 */ 1169 public static int floorDiv(int x, int y) { 1170 int r = x / y; 1171 // if the signs are different and modulo not zero, round down 1172 if ((x ^ y) < 0 && (r * y != x)) { 1173 r--; 1174 } 1175 return r; 1176 } 1177 1178 /** 1179 * Returns the largest (closest to positive infinity) 1180 * {@code long} value that is less than or equal to the algebraic quotient. 1181 * There is one special case, if the dividend is the 1182 * {@linkplain Long#MIN_VALUE Long.MIN_VALUE} and the divisor is {@code -1}, 1183 * then integer overflow occurs and 1184 * the result is equal to {@code Long.MIN_VALUE}. 1185 * <p> 1186 * Normal integer division operates under the round to zero rounding mode 1187 * (truncation). This operation instead acts under the round toward 1188 * negative infinity (floor) rounding mode. 1189 * The floor rounding mode gives different results from truncation 1190 * when the exact result is negative. 1191 * <p> 1192 * For examples, see {@link #floorDiv(int, int)}. 1193 * 1194 * @param x the dividend 1195 * @param y the divisor 1196 * @return the largest (closest to positive infinity) 1197 * {@code int} value that is less than or equal to the algebraic quotient. 1198 * @throws ArithmeticException if the divisor {@code y} is zero 1199 * @see #floorMod(long, int) 1200 * @see #floor(double) 1201 * @since 9 1202 */ 1203 public static long floorDiv(long x, int y) { 1204 return floorDiv(x, (long)y); 1205 } 1206 1207 /** 1208 * Returns the largest (closest to positive infinity) 1209 * {@code long} value that is less than or equal to the algebraic quotient. 1210 * There is one special case, if the dividend is the 1211 * {@linkplain Long#MIN_VALUE Long.MIN_VALUE} and the divisor is {@code -1}, 1212 * then integer overflow occurs and 1213 * the result is equal to {@code Long.MIN_VALUE}. 1214 * <p> 1215 * Normal integer division operates under the round to zero rounding mode 1216 * (truncation). This operation instead acts under the round toward 1217 * negative infinity (floor) rounding mode. 1218 * The floor rounding mode gives different results from truncation 1219 * when the exact result is negative. 1220 * <p> 1221 * For examples, see {@link #floorDiv(int, int)}. 1222 * 1223 * @param x the dividend 1224 * @param y the divisor 1225 * @return the largest (closest to positive infinity) 1226 * {@code long} value that is less than or equal to the algebraic quotient. 1227 * @throws ArithmeticException if the divisor {@code y} is zero 1228 * @see #floorMod(long, long) 1229 * @see #floor(double) 1230 * @since 1.8 1231 */ 1232 public static long floorDiv(long x, long y) { 1233 long r = x / y; 1234 // if the signs are different and modulo not zero, round down 1235 if ((x ^ y) < 0 && (r * y != x)) { 1236 r--; 1237 } 1238 return r; 1239 } 1240 1241 /** 1242 * Returns the floor modulus of the {@code int} arguments. 1243 * <p> 1244 * The floor modulus is {@code x - (floorDiv(x, y) * y)}, 1245 * has the same sign as the divisor {@code y}, and 1246 * is in the range of {@code -abs(y) < r < +abs(y)}. 1247 * 1248 * <p> 1249 * The relationship between {@code floorDiv} and {@code floorMod} is such that: 1250 * <ul> 1251 * <li>{@code floorDiv(x, y) * y + floorMod(x, y) == x} 1252 * </ul> 1253 * <p> 1254 * The difference in values between {@code floorMod} and 1255 * the {@code %} operator is due to the difference between 1256 * {@code floorDiv} that returns the integer less than or equal to the quotient 1257 * and the {@code /} operator that returns the integer closest to zero. 1258 * <p> 1259 * Examples: 1260 * <ul> 1261 * <li>If the signs of the arguments are the same, the results 1262 * of {@code floorMod} and the {@code %} operator are the same.<br> 1263 * <ul> 1264 * <li>{@code floorMod(+4, +3) == +1}; and {@code (+4 % +3) == +1}</li> 1265 * <li>{@code floorMod(-4, -3) == -1}; and {@code (-4 % -3) == -1}</li> 1266 * </ul> 1267 * <li>If the signs of the arguments are different, the results 1268 * differ from the {@code %} operator.<br> 1269 * <ul> 1270 * <li>{@code floorMod(+4, -3) == -2}; and {@code (+4 % -3) == +1}</li> 1271 * <li>{@code floorMod(-4, +3) == +2}; and {@code (-4 % +3) == -1}</li> 1272 * </ul> 1273 * </li> 1274 * </ul> 1275 * <p> 1276 * If the signs of arguments are unknown and a positive modulus 1277 * is needed it can be computed as {@code (floorMod(x, y) + abs(y)) % abs(y)}. 1278 * 1279 * @param x the dividend 1280 * @param y the divisor 1281 * @return the floor modulus {@code x - (floorDiv(x, y) * y)} 1282 * @throws ArithmeticException if the divisor {@code y} is zero 1283 * @see #floorDiv(int, int) 1284 * @since 1.8 1285 */ 1286 public static int floorMod(int x, int y) { 1287 int mod = x % y; 1288 // if the signs are different and modulo not zero, adjust result 1289 if ((mod ^ y) < 0 && mod != 0) { 1290 mod += y; 1291 } 1292 return mod; 1293 } 1294 1295 /** 1296 * Returns the floor modulus of the {@code long} and {@code int} arguments. 1297 * <p> 1298 * The floor modulus is {@code x - (floorDiv(x, y) * y)}, 1299 * has the same sign as the divisor {@code y}, and 1300 * is in the range of {@code -abs(y) < r < +abs(y)}. 1301 * 1302 * <p> 1303 * The relationship between {@code floorDiv} and {@code floorMod} is such that: 1304 * <ul> 1305 * <li>{@code floorDiv(x, y) * y + floorMod(x, y) == x} 1306 * </ul> 1307 * <p> 1308 * For examples, see {@link #floorMod(int, int)}. 1309 * 1310 * @param x the dividend 1311 * @param y the divisor 1312 * @return the floor modulus {@code x - (floorDiv(x, y) * y)} 1313 * @throws ArithmeticException if the divisor {@code y} is zero 1314 * @see #floorDiv(long, int) 1315 * @since 9 1316 */ 1317 public static int floorMod(long x, int y) { 1318 // Result cannot overflow the range of int. 1319 return (int)floorMod(x, (long)y); 1320 } 1321 1322 /** 1323 * Returns the floor modulus of the {@code long} arguments. 1324 * <p> 1325 * The floor modulus is {@code x - (floorDiv(x, y) * y)}, 1326 * has the same sign as the divisor {@code y}, and 1327 * is in the range of {@code -abs(y) < r < +abs(y)}. 1328 * 1329 * <p> 1330 * The relationship between {@code floorDiv} and {@code floorMod} is such that: 1331 * <ul> 1332 * <li>{@code floorDiv(x, y) * y + floorMod(x, y) == x} 1333 * </ul> 1334 * <p> 1335 * For examples, see {@link #floorMod(int, int)}. 1336 * 1337 * @param x the dividend 1338 * @param y the divisor 1339 * @return the floor modulus {@code x - (floorDiv(x, y) * y)} 1340 * @throws ArithmeticException if the divisor {@code y} is zero 1341 * @see #floorDiv(long, long) 1342 * @since 1.8 1343 */ 1344 public static long floorMod(long x, long y) { 1345 long mod = x % y; 1346 // if the signs are different and modulo not zero, adjust result 1347 if ((x ^ y) < 0 && mod != 0) { 1348 mod += y; 1349 } 1350 return mod; 1351 } 1352 1353 /** 1354 * Returns the absolute value of an {@code int} value. 1355 * If the argument is not negative, the argument is returned. 1356 * If the argument is negative, the negation of the argument is returned. 1357 * 1358 * <p>Note that if the argument is equal to the value of 1359 * {@link Integer#MIN_VALUE}, the most negative representable 1360 * {@code int} value, the result is that same value, which is 1361 * negative. 1362 * 1363 * @param a the argument whose absolute value is to be determined 1364 * @return the absolute value of the argument. 1365 */ 1366 @HotSpotIntrinsicCandidate 1367 public static int abs(int a) { 1368 return (a < 0) ? -a : a; 1369 } 1370 1371 /** 1372 * Returns the absolute value of a {@code long} value. 1373 * If the argument is not negative, the argument is returned. 1374 * If the argument is negative, the negation of the argument is returned. 1375 * 1376 * <p>Note that if the argument is equal to the value of 1377 * {@link Long#MIN_VALUE}, the most negative representable 1378 * {@code long} value, the result is that same value, which 1379 * is negative. 1380 * 1381 * @param a the argument whose absolute value is to be determined 1382 * @return the absolute value of the argument. 1383 */ 1384 @HotSpotIntrinsicCandidate 1385 public static long abs(long a) { 1386 return (a < 0) ? -a : a; 1387 } 1388 1389 /** 1390 * Returns the absolute value of a {@code float} value. 1391 * If the argument is not negative, the argument is returned. 1392 * If the argument is negative, the negation of the argument is returned. 1393 * Special cases: 1394 * <ul><li>If the argument is positive zero or negative zero, the 1395 * result is positive zero. 1396 * <li>If the argument is infinite, the result is positive infinity. 1397 * <li>If the argument is NaN, the result is NaN.</ul> 1398 * 1399 * @apiNote As implied by the above, one valid implementation of 1400 * this method is given by the expression below which computes a 1401 * {@code float} with the same exponent and significand as the 1402 * argument but with a guaranteed zero sign bit indicating a 1403 * positive value:<br> 1404 * {@code Float.intBitsToFloat(0x7fffffff & Float.floatToRawIntBits(a))} 1405 * 1406 * @param a the argument whose absolute value is to be determined 1407 * @return the absolute value of the argument. 1408 */ 1409 @HotSpotIntrinsicCandidate 1410 public static float abs(float a) { 1411 return (a <= 0.0F) ? 0.0F - a : a; 1412 } 1413 1414 /** 1415 * Returns the absolute value of a {@code double} value. 1416 * If the argument is not negative, the argument is returned. 1417 * If the argument is negative, the negation of the argument is returned. 1418 * Special cases: 1419 * <ul><li>If the argument is positive zero or negative zero, the result 1420 * is positive zero. 1421 * <li>If the argument is infinite, the result is positive infinity. 1422 * <li>If the argument is NaN, the result is NaN.</ul> 1423 * 1424 * @apiNote As implied by the above, one valid implementation of 1425 * this method is given by the expression below which computes a 1426 * {@code double} with the same exponent and significand as the 1427 * argument but with a guaranteed zero sign bit indicating a 1428 * positive value:<br> 1429 * {@code Double.longBitsToDouble((Double.doubleToRawLongBits(a)<<1)>>>1)} 1430 * 1431 * @param a the argument whose absolute value is to be determined 1432 * @return the absolute value of the argument. 1433 */ 1434 @HotSpotIntrinsicCandidate 1435 public static double abs(double a) { 1436 return (a <= 0.0D) ? 0.0D - a : a; 1437 } 1438 1439 /** 1440 * Returns the greater of two {@code int} values. That is, the 1441 * result is the argument closer to the value of 1442 * {@link Integer#MAX_VALUE}. If the arguments have the same value, 1443 * the result is that same value. 1444 * 1445 * @param a an argument. 1446 * @param b another argument. 1447 * @return the larger of {@code a} and {@code b}. 1448 */ 1449 @HotSpotIntrinsicCandidate 1450 public static int max(int a, int b) { 1451 return (a >= b) ? a : b; 1452 } 1453 1454 /** 1455 * Returns the greater of two {@code long} values. That is, the 1456 * result is the argument closer to the value of 1457 * {@link Long#MAX_VALUE}. If the arguments have the same value, 1458 * the result is that same value. 1459 * 1460 * @param a an argument. 1461 * @param b another argument. 1462 * @return the larger of {@code a} and {@code b}. 1463 */ 1464 public static long max(long a, long b) { 1465 return (a >= b) ? a : b; 1466 } 1467 1468 // Use raw bit-wise conversions on guaranteed non-NaN arguments. 1469 private static final long negativeZeroFloatBits = Float.floatToRawIntBits(-0.0f); 1470 private static final long negativeZeroDoubleBits = Double.doubleToRawLongBits(-0.0d); 1471 1472 /** 1473 * Returns the greater of two {@code float} values. That is, 1474 * the result is the argument closer to positive infinity. If the 1475 * arguments have the same value, the result is that same 1476 * value. If either value is NaN, then the result is NaN. Unlike 1477 * the numerical comparison operators, this method considers 1478 * negative zero to be strictly smaller than positive zero. If one 1479 * argument is positive zero and the other negative zero, the 1480 * result is positive zero. 1481 * 1482 * @param a an argument. 1483 * @param b another argument. 1484 * @return the larger of {@code a} and {@code b}. 1485 */ 1486 @HotSpotIntrinsicCandidate 1487 public static float max(float a, float b) { 1488 if (a != a) 1489 return a; // a is NaN 1490 if ((a == 0.0f) && 1491 (b == 0.0f) && 1492 (Float.floatToRawIntBits(a) == negativeZeroFloatBits)) { 1493 // Raw conversion ok since NaN can't map to -0.0. 1494 return b; 1495 } 1496 return (a >= b) ? a : b; 1497 } 1498 1499 /** 1500 * Returns the greater of two {@code double} values. That 1501 * is, the result is the argument closer to positive infinity. If 1502 * the arguments have the same value, the result is that same 1503 * value. If either value is NaN, then the result is NaN. Unlike 1504 * the numerical comparison operators, this method considers 1505 * negative zero to be strictly smaller than positive zero. If one 1506 * argument is positive zero and the other negative zero, the 1507 * result is positive zero. 1508 * 1509 * @param a an argument. 1510 * @param b another argument. 1511 * @return the larger of {@code a} and {@code b}. 1512 */ 1513 @HotSpotIntrinsicCandidate 1514 public static double max(double a, double b) { 1515 if (a != a) 1516 return a; // a is NaN 1517 if ((a == 0.0d) && 1518 (b == 0.0d) && 1519 (Double.doubleToRawLongBits(a) == negativeZeroDoubleBits)) { 1520 // Raw conversion ok since NaN can't map to -0.0. 1521 return b; 1522 } 1523 return (a >= b) ? a : b; 1524 } 1525 1526 /** 1527 * Returns the smaller of two {@code int} values. That is, 1528 * the result the argument closer to the value of 1529 * {@link Integer#MIN_VALUE}. If the arguments have the same 1530 * value, the result is that same value. 1531 * 1532 * @param a an argument. 1533 * @param b another argument. 1534 * @return the smaller of {@code a} and {@code b}. 1535 */ 1536 @HotSpotIntrinsicCandidate 1537 public static int min(int a, int b) { 1538 return (a <= b) ? a : b; 1539 } 1540 1541 /** 1542 * Returns the smaller of two {@code long} values. That is, 1543 * the result is the argument closer to the value of 1544 * {@link Long#MIN_VALUE}. If the arguments have the same 1545 * value, the result is that same value. 1546 * 1547 * @param a an argument. 1548 * @param b another argument. 1549 * @return the smaller of {@code a} and {@code b}. 1550 */ 1551 public static long min(long a, long b) { 1552 return (a <= b) ? a : b; 1553 } 1554 1555 /** 1556 * Returns the smaller of two {@code float} values. That is, 1557 * the result is the value closer to negative infinity. If the 1558 * arguments have the same value, the result is that same 1559 * value. If either value is NaN, then the result is NaN. Unlike 1560 * the numerical comparison operators, this method considers 1561 * negative zero to be strictly smaller than positive zero. If 1562 * one argument is positive zero and the other is negative zero, 1563 * the result is negative zero. 1564 * 1565 * @param a an argument. 1566 * @param b another argument. 1567 * @return the smaller of {@code a} and {@code b}. 1568 */ 1569 @HotSpotIntrinsicCandidate 1570 public static float min(float a, float b) { 1571 if (a != a) 1572 return a; // a is NaN 1573 if ((a == 0.0f) && 1574 (b == 0.0f) && 1575 (Float.floatToRawIntBits(b) == negativeZeroFloatBits)) { 1576 // Raw conversion ok since NaN can't map to -0.0. 1577 return b; 1578 } 1579 return (a <= b) ? a : b; 1580 } 1581 1582 /** 1583 * Returns the smaller of two {@code double} values. That 1584 * is, the result is the value closer to negative infinity. If the 1585 * arguments have the same value, the result is that same 1586 * value. If either value is NaN, then the result is NaN. Unlike 1587 * the numerical comparison operators, this method considers 1588 * negative zero to be strictly smaller than positive zero. If one 1589 * argument is positive zero and the other is negative zero, the 1590 * result is negative zero. 1591 * 1592 * @param a an argument. 1593 * @param b another argument. 1594 * @return the smaller of {@code a} and {@code b}. 1595 */ 1596 @HotSpotIntrinsicCandidate 1597 public static double min(double a, double b) { 1598 if (a != a) 1599 return a; // a is NaN 1600 if ((a == 0.0d) && 1601 (b == 0.0d) && 1602 (Double.doubleToRawLongBits(b) == negativeZeroDoubleBits)) { 1603 // Raw conversion ok since NaN can't map to -0.0. 1604 return b; 1605 } 1606 return (a <= b) ? a : b; 1607 } 1608 1609 /** 1610 * Returns the fused multiply add of the three arguments; that is, 1611 * returns the exact product of the first two arguments summed 1612 * with the third argument and then rounded once to the nearest 1613 * {@code double}. 1614 * 1615 * The rounding is done using the {@linkplain 1616 * java.math.RoundingMode#HALF_EVEN round to nearest even 1617 * rounding mode}. 1618 * 1619 * In contrast, if {@code a * b + c} is evaluated as a regular 1620 * floating-point expression, two rounding errors are involved, 1621 * the first for the multiply operation, the second for the 1622 * addition operation. 1623 * 1624 * <p>Special cases: 1625 * <ul> 1626 * <li> If any argument is NaN, the result is NaN. 1627 * 1628 * <li> If one of the first two arguments is infinite and the 1629 * other is zero, the result is NaN. 1630 * 1631 * <li> If the exact product of the first two arguments is infinite 1632 * (in other words, at least one of the arguments is infinite and 1633 * the other is neither zero nor NaN) and the third argument is an 1634 * infinity of the opposite sign, the result is NaN. 1635 * 1636 * </ul> 1637 * 1638 * <p>Note that {@code fma(a, 1.0, c)} returns the same 1639 * result as ({@code a + c}). However, 1640 * {@code fma(a, b, +0.0)} does <em>not</em> always return the 1641 * same result as ({@code a * b}) since 1642 * {@code fma(-0.0, +0.0, +0.0)} is {@code +0.0} while 1643 * ({@code -0.0 * +0.0}) is {@code -0.0}; {@code fma(a, b, -0.0)} is 1644 * equivalent to ({@code a * b}) however. 1645 * 1646 * @apiNote This method corresponds to the fusedMultiplyAdd 1647 * operation defined in IEEE 754-2008. 1648 * 1649 * @param a a value 1650 * @param b a value 1651 * @param c a value 1652 * 1653 * @return (<i>a</i> × <i>b</i> + <i>c</i>) 1654 * computed, as if with unlimited range and precision, and rounded 1655 * once to the nearest {@code double} value 1656 * 1657 * @since 9 1658 */ 1659 @HotSpotIntrinsicCandidate 1660 public static double fma(double a, double b, double c) { 1661 /* 1662 * Infinity and NaN arithmetic is not quite the same with two 1663 * roundings as opposed to just one so the simple expression 1664 * "a * b + c" cannot always be used to compute the correct 1665 * result. With two roundings, the product can overflow and 1666 * if the addend is infinite, a spurious NaN can be produced 1667 * if the infinity from the overflow and the infinite addend 1668 * have opposite signs. 1669 */ 1670 1671 // First, screen for and handle non-finite input values whose 1672 // arithmetic is not supported by BigDecimal. 1673 if (Double.isNaN(a) || Double.isNaN(b) || Double.isNaN(c)) { 1674 return Double.NaN; 1675 } else { // All inputs non-NaN 1676 boolean infiniteA = Double.isInfinite(a); 1677 boolean infiniteB = Double.isInfinite(b); 1678 boolean infiniteC = Double.isInfinite(c); 1679 double result; 1680 1681 if (infiniteA || infiniteB || infiniteC) { 1682 if (infiniteA && b == 0.0 || 1683 infiniteB && a == 0.0 ) { 1684 return Double.NaN; 1685 } 1686 // Store product in a double field to cause an 1687 // overflow even if non-strictfp evaluation is being 1688 // used. 1689 double product = a * b; 1690 if (Double.isInfinite(product) && !infiniteA && !infiniteB) { 1691 // Intermediate overflow; might cause a 1692 // spurious NaN if added to infinite c. 1693 assert Double.isInfinite(c); 1694 return c; 1695 } else { 1696 result = product + c; 1697 assert !Double.isFinite(result); 1698 return result; 1699 } 1700 } else { // All inputs finite 1701 BigDecimal product = (new BigDecimal(a)).multiply(new BigDecimal(b)); 1702 if (c == 0.0) { // Positive or negative zero 1703 // If the product is an exact zero, use a 1704 // floating-point expression to compute the sign 1705 // of the zero final result. The product is an 1706 // exact zero if and only if at least one of a and 1707 // b is zero. 1708 if (a == 0.0 || b == 0.0) { 1709 return a * b + c; 1710 } else { 1711 // The sign of a zero addend doesn't matter if 1712 // the product is nonzero. The sign of a zero 1713 // addend is not factored in the result if the 1714 // exact product is nonzero but underflows to 1715 // zero; see IEEE-754 2008 section 6.3 "The 1716 // sign bit". 1717 return product.doubleValue(); 1718 } 1719 } else { 1720 return product.add(new BigDecimal(c)).doubleValue(); 1721 } 1722 } 1723 } 1724 } 1725 1726 /** 1727 * Returns the fused multiply add of the three arguments; that is, 1728 * returns the exact product of the first two arguments summed 1729 * with the third argument and then rounded once to the nearest 1730 * {@code float}. 1731 * 1732 * The rounding is done using the {@linkplain 1733 * java.math.RoundingMode#HALF_EVEN round to nearest even 1734 * rounding mode}. 1735 * 1736 * In contrast, if {@code a * b + c} is evaluated as a regular 1737 * floating-point expression, two rounding errors are involved, 1738 * the first for the multiply operation, the second for the 1739 * addition operation. 1740 * 1741 * <p>Special cases: 1742 * <ul> 1743 * <li> If any argument is NaN, the result is NaN. 1744 * 1745 * <li> If one of the first two arguments is infinite and the 1746 * other is zero, the result is NaN. 1747 * 1748 * <li> If the exact product of the first two arguments is infinite 1749 * (in other words, at least one of the arguments is infinite and 1750 * the other is neither zero nor NaN) and the third argument is an 1751 * infinity of the opposite sign, the result is NaN. 1752 * 1753 * </ul> 1754 * 1755 * <p>Note that {@code fma(a, 1.0f, c)} returns the same 1756 * result as ({@code a + c}). However, 1757 * {@code fma(a, b, +0.0f)} does <em>not</em> always return the 1758 * same result as ({@code a * b}) since 1759 * {@code fma(-0.0f, +0.0f, +0.0f)} is {@code +0.0f} while 1760 * ({@code -0.0f * +0.0f}) is {@code -0.0f}; {@code fma(a, b, -0.0f)} is 1761 * equivalent to ({@code a * b}) however. 1762 * 1763 * @apiNote This method corresponds to the fusedMultiplyAdd 1764 * operation defined in IEEE 754-2008. 1765 * 1766 * @param a a value 1767 * @param b a value 1768 * @param c a value 1769 * 1770 * @return (<i>a</i> × <i>b</i> + <i>c</i>) 1771 * computed, as if with unlimited range and precision, and rounded 1772 * once to the nearest {@code float} value 1773 * 1774 * @since 9 1775 */ 1776 @HotSpotIntrinsicCandidate 1777 public static float fma(float a, float b, float c) { 1778 /* 1779 * Since the double format has more than twice the precision 1780 * of the float format, the multiply of a * b is exact in 1781 * double. The add of c to the product then incurs one 1782 * rounding error. Since the double format moreover has more 1783 * than (2p + 2) precision bits compared to the p bits of the 1784 * float format, the two roundings of (a * b + c), first to 1785 * the double format and then secondarily to the float format, 1786 * are equivalent to rounding the intermediate result directly 1787 * to the float format. 1788 * 1789 * In terms of strictfp vs default-fp concerns related to 1790 * overflow and underflow, since 1791 * 1792 * (Float.MAX_VALUE * Float.MAX_VALUE) << Double.MAX_VALUE 1793 * (Float.MIN_VALUE * Float.MIN_VALUE) >> Double.MIN_VALUE 1794 * 1795 * neither the multiply nor add will overflow or underflow in 1796 * double. Therefore, it is not necessary for this method to 1797 * be declared strictfp to have reproducible 1798 * behavior. However, it is necessary to explicitly store down 1799 * to a float variable to avoid returning a value in the float 1800 * extended value set. 1801 */ 1802 float result = (float)(((double) a * (double) b ) + (double) c); 1803 return result; 1804 } 1805 1806 /** 1807 * Returns the size of an ulp of the argument. An ulp, unit in 1808 * the last place, of a {@code double} value is the positive 1809 * distance between this floating-point value and the {@code 1810 * double} value next larger in magnitude. Note that for non-NaN 1811 * <i>x</i>, <code>ulp(-<i>x</i>) == ulp(<i>x</i>)</code>. 1812 * 1813 * <p>Special Cases: 1814 * <ul> 1815 * <li> If the argument is NaN, then the result is NaN. 1816 * <li> If the argument is positive or negative infinity, then the 1817 * result is positive infinity. 1818 * <li> If the argument is positive or negative zero, then the result is 1819 * {@code Double.MIN_VALUE}. 1820 * <li> If the argument is ±{@code Double.MAX_VALUE}, then 1821 * the result is equal to 2<sup>971</sup>. 1822 * </ul> 1823 * 1824 * @param d the floating-point value whose ulp is to be returned 1825 * @return the size of an ulp of the argument 1826 * @author Joseph D. Darcy 1827 * @since 1.5 1828 */ 1829 public static double ulp(double d) { 1830 int exp = getExponent(d); 1831 1832 switch(exp) { 1833 case Double.MAX_EXPONENT + 1: // NaN or infinity 1834 return Math.abs(d); 1835 1836 case Double.MIN_EXPONENT - 1: // zero or subnormal 1837 return Double.MIN_VALUE; 1838 1839 default: 1840 assert exp <= Double.MAX_EXPONENT && exp >= Double.MIN_EXPONENT; 1841 1842 // ulp(x) is usually 2^(SIGNIFICAND_WIDTH-1)*(2^ilogb(x)) 1843 exp = exp - (DoubleConsts.SIGNIFICAND_WIDTH-1); 1844 if (exp >= Double.MIN_EXPONENT) { 1845 return powerOfTwoD(exp); 1846 } 1847 else { 1848 // return a subnormal result; left shift integer 1849 // representation of Double.MIN_VALUE appropriate 1850 // number of positions 1851 return Double.longBitsToDouble(1L << 1852 (exp - (Double.MIN_EXPONENT - (DoubleConsts.SIGNIFICAND_WIDTH-1)) )); 1853 } 1854 } 1855 } 1856 1857 /** 1858 * Returns the size of an ulp of the argument. An ulp, unit in 1859 * the last place, of a {@code float} value is the positive 1860 * distance between this floating-point value and the {@code 1861 * float} value next larger in magnitude. Note that for non-NaN 1862 * <i>x</i>, <code>ulp(-<i>x</i>) == ulp(<i>x</i>)</code>. 1863 * 1864 * <p>Special Cases: 1865 * <ul> 1866 * <li> If the argument is NaN, then the result is NaN. 1867 * <li> If the argument is positive or negative infinity, then the 1868 * result is positive infinity. 1869 * <li> If the argument is positive or negative zero, then the result is 1870 * {@code Float.MIN_VALUE}. 1871 * <li> If the argument is ±{@code Float.MAX_VALUE}, then 1872 * the result is equal to 2<sup>104</sup>. 1873 * </ul> 1874 * 1875 * @param f the floating-point value whose ulp is to be returned 1876 * @return the size of an ulp of the argument 1877 * @author Joseph D. Darcy 1878 * @since 1.5 1879 */ 1880 public static float ulp(float f) { 1881 int exp = getExponent(f); 1882 1883 switch(exp) { 1884 case Float.MAX_EXPONENT+1: // NaN or infinity 1885 return Math.abs(f); 1886 1887 case Float.MIN_EXPONENT-1: // zero or subnormal 1888 return Float.MIN_VALUE; 1889 1890 default: 1891 assert exp <= Float.MAX_EXPONENT && exp >= Float.MIN_EXPONENT; 1892 1893 // ulp(x) is usually 2^(SIGNIFICAND_WIDTH-1)*(2^ilogb(x)) 1894 exp = exp - (FloatConsts.SIGNIFICAND_WIDTH-1); 1895 if (exp >= Float.MIN_EXPONENT) { 1896 return powerOfTwoF(exp); 1897 } else { 1898 // return a subnormal result; left shift integer 1899 // representation of FloatConsts.MIN_VALUE appropriate 1900 // number of positions 1901 return Float.intBitsToFloat(1 << 1902 (exp - (Float.MIN_EXPONENT - (FloatConsts.SIGNIFICAND_WIDTH-1)) )); 1903 } 1904 } 1905 } 1906 1907 /** 1908 * Returns the signum function of the argument; zero if the argument 1909 * is zero, 1.0 if the argument is greater than zero, -1.0 if the 1910 * argument is less than zero. 1911 * 1912 * <p>Special Cases: 1913 * <ul> 1914 * <li> If the argument is NaN, then the result is NaN. 1915 * <li> If the argument is positive zero or negative zero, then the 1916 * result is the same as the argument. 1917 * </ul> 1918 * 1919 * @param d the floating-point value whose signum is to be returned 1920 * @return the signum function of the argument 1921 * @author Joseph D. Darcy 1922 * @since 1.5 1923 */ 1924 public static double signum(double d) { 1925 return (d == 0.0 || Double.isNaN(d))?d:copySign(1.0, d); 1926 } 1927 1928 /** 1929 * Returns the signum function of the argument; zero if the argument 1930 * is zero, 1.0f if the argument is greater than zero, -1.0f if the 1931 * argument is less than zero. 1932 * 1933 * <p>Special Cases: 1934 * <ul> 1935 * <li> If the argument is NaN, then the result is NaN. 1936 * <li> If the argument is positive zero or negative zero, then the 1937 * result is the same as the argument. 1938 * </ul> 1939 * 1940 * @param f the floating-point value whose signum is to be returned 1941 * @return the signum function of the argument 1942 * @author Joseph D. Darcy 1943 * @since 1.5 1944 */ 1945 public static float signum(float f) { 1946 return (f == 0.0f || Float.isNaN(f))?f:copySign(1.0f, f); 1947 } 1948 1949 /** 1950 * Returns the hyperbolic sine of a {@code double} value. 1951 * The hyperbolic sine of <i>x</i> is defined to be 1952 * (<i>e<sup>x</sup> - e<sup>-x</sup></i>)/2 1953 * where <i>e</i> is {@linkplain Math#E Euler's number}. 1954 * 1955 * <p>Special cases: 1956 * <ul> 1957 * 1958 * <li>If the argument is NaN, then the result is NaN. 1959 * 1960 * <li>If the argument is infinite, then the result is an infinity 1961 * with the same sign as the argument. 1962 * 1963 * <li>If the argument is zero, then the result is a zero with the 1964 * same sign as the argument. 1965 * 1966 * </ul> 1967 * 1968 * <p>The computed result must be within 2.5 ulps of the exact result. 1969 * 1970 * @param x The number whose hyperbolic sine is to be returned. 1971 * @return The hyperbolic sine of {@code x}. 1972 * @since 1.5 1973 */ 1974 public static double sinh(double x) { 1975 return StrictMath.sinh(x); 1976 } 1977 1978 /** 1979 * Returns the hyperbolic cosine of a {@code double} value. 1980 * The hyperbolic cosine of <i>x</i> is defined to be 1981 * (<i>e<sup>x</sup> + e<sup>-x</sup></i>)/2 1982 * where <i>e</i> is {@linkplain Math#E Euler's number}. 1983 * 1984 * <p>Special cases: 1985 * <ul> 1986 * 1987 * <li>If the argument is NaN, then the result is NaN. 1988 * 1989 * <li>If the argument is infinite, then the result is positive 1990 * infinity. 1991 * 1992 * <li>If the argument is zero, then the result is {@code 1.0}. 1993 * 1994 * </ul> 1995 * 1996 * <p>The computed result must be within 2.5 ulps of the exact result. 1997 * 1998 * @param x The number whose hyperbolic cosine is to be returned. 1999 * @return The hyperbolic cosine of {@code x}. 2000 * @since 1.5 2001 */ 2002 public static double cosh(double x) { 2003 return StrictMath.cosh(x); 2004 } 2005 2006 /** 2007 * Returns the hyperbolic tangent of a {@code double} value. 2008 * The hyperbolic tangent of <i>x</i> is defined to be 2009 * (<i>e<sup>x</sup> - e<sup>-x</sup></i>)/(<i>e<sup>x</sup> + e<sup>-x</sup></i>), 2010 * in other words, {@linkplain Math#sinh 2011 * sinh(<i>x</i>)}/{@linkplain Math#cosh cosh(<i>x</i>)}. Note 2012 * that the absolute value of the exact tanh is always less than 2013 * 1. 2014 * 2015 * <p>Special cases: 2016 * <ul> 2017 * 2018 * <li>If the argument is NaN, then the result is NaN. 2019 * 2020 * <li>If the argument is zero, then the result is a zero with the 2021 * same sign as the argument. 2022 * 2023 * <li>If the argument is positive infinity, then the result is 2024 * {@code +1.0}. 2025 * 2026 * <li>If the argument is negative infinity, then the result is 2027 * {@code -1.0}. 2028 * 2029 * </ul> 2030 * 2031 * <p>The computed result must be within 2.5 ulps of the exact result. 2032 * The result of {@code tanh} for any finite input must have 2033 * an absolute value less than or equal to 1. Note that once the 2034 * exact result of tanh is within 1/2 of an ulp of the limit value 2035 * of ±1, correctly signed ±{@code 1.0} should 2036 * be returned. 2037 * 2038 * @param x The number whose hyperbolic tangent is to be returned. 2039 * @return The hyperbolic tangent of {@code x}. 2040 * @since 1.5 2041 */ 2042 public static double tanh(double x) { 2043 return StrictMath.tanh(x); 2044 } 2045 2046 /** 2047 * Returns sqrt(<i>x</i><sup>2</sup> +<i>y</i><sup>2</sup>) 2048 * without intermediate overflow or underflow. 2049 * 2050 * <p>Special cases: 2051 * <ul> 2052 * 2053 * <li> If either argument is infinite, then the result 2054 * is positive infinity. 2055 * 2056 * <li> If either argument is NaN and neither argument is infinite, 2057 * then the result is NaN. 2058 * 2059 * </ul> 2060 * 2061 * <p>The computed result must be within 1 ulp of the exact 2062 * result. If one parameter is held constant, the results must be 2063 * semi-monotonic in the other parameter. 2064 * 2065 * @param x a value 2066 * @param y a value 2067 * @return sqrt(<i>x</i><sup>2</sup> +<i>y</i><sup>2</sup>) 2068 * without intermediate overflow or underflow 2069 * @since 1.5 2070 */ 2071 public static double hypot(double x, double y) { 2072 return StrictMath.hypot(x, y); 2073 } 2074 2075 /** 2076 * Returns <i>e</i><sup>x</sup> -1. Note that for values of 2077 * <i>x</i> near 0, the exact sum of 2078 * {@code expm1(x)} + 1 is much closer to the true 2079 * result of <i>e</i><sup>x</sup> than {@code exp(x)}. 2080 * 2081 * <p>Special cases: 2082 * <ul> 2083 * <li>If the argument is NaN, the result is NaN. 2084 * 2085 * <li>If the argument is positive infinity, then the result is 2086 * positive infinity. 2087 * 2088 * <li>If the argument is negative infinity, then the result is 2089 * -1.0. 2090 * 2091 * <li>If the argument is zero, then the result is a zero with the 2092 * same sign as the argument. 2093 * 2094 * </ul> 2095 * 2096 * <p>The computed result must be within 1 ulp of the exact result. 2097 * Results must be semi-monotonic. The result of 2098 * {@code expm1} for any finite input must be greater than or 2099 * equal to {@code -1.0}. Note that once the exact result of 2100 * <i>e</i><sup>{@code x}</sup> - 1 is within 1/2 2101 * ulp of the limit value -1, {@code -1.0} should be 2102 * returned. 2103 * 2104 * @param x the exponent to raise <i>e</i> to in the computation of 2105 * <i>e</i><sup>{@code x}</sup> -1. 2106 * @return the value <i>e</i><sup>{@code x}</sup> - 1. 2107 * @since 1.5 2108 */ 2109 public static double expm1(double x) { 2110 return StrictMath.expm1(x); 2111 } 2112 2113 /** 2114 * Returns the natural logarithm of the sum of the argument and 1. 2115 * Note that for small values {@code x}, the result of 2116 * {@code log1p(x)} is much closer to the true result of ln(1 2117 * + {@code x}) than the floating-point evaluation of 2118 * {@code log(1.0+x)}. 2119 * 2120 * <p>Special cases: 2121 * 2122 * <ul> 2123 * 2124 * <li>If the argument is NaN or less than -1, then the result is 2125 * NaN. 2126 * 2127 * <li>If the argument is positive infinity, then the result is 2128 * positive infinity. 2129 * 2130 * <li>If the argument is negative one, then the result is 2131 * negative infinity. 2132 * 2133 * <li>If the argument is zero, then the result is a zero with the 2134 * same sign as the argument. 2135 * 2136 * </ul> 2137 * 2138 * <p>The computed result must be within 1 ulp of the exact result. 2139 * Results must be semi-monotonic. 2140 * 2141 * @param x a value 2142 * @return the value ln({@code x} + 1), the natural 2143 * log of {@code x} + 1 2144 * @since 1.5 2145 */ 2146 public static double log1p(double x) { 2147 return StrictMath.log1p(x); 2148 } 2149 2150 /** 2151 * Returns the first floating-point argument with the sign of the 2152 * second floating-point argument. Note that unlike the {@link 2153 * StrictMath#copySign(double, double) StrictMath.copySign} 2154 * method, this method does not require NaN {@code sign} 2155 * arguments to be treated as positive values; implementations are 2156 * permitted to treat some NaN arguments as positive and other NaN 2157 * arguments as negative to allow greater performance. 2158 * 2159 * @param magnitude the parameter providing the magnitude of the result 2160 * @param sign the parameter providing the sign of the result 2161 * @return a value with the magnitude of {@code magnitude} 2162 * and the sign of {@code sign}. 2163 * @since 1.6 2164 */ 2165 public static double copySign(double magnitude, double sign) { 2166 return Double.longBitsToDouble((Double.doubleToRawLongBits(sign) & 2167 (DoubleConsts.SIGN_BIT_MASK)) | 2168 (Double.doubleToRawLongBits(magnitude) & 2169 (DoubleConsts.EXP_BIT_MASK | 2170 DoubleConsts.SIGNIF_BIT_MASK))); 2171 } 2172 2173 /** 2174 * Returns the first floating-point argument with the sign of the 2175 * second floating-point argument. Note that unlike the {@link 2176 * StrictMath#copySign(float, float) StrictMath.copySign} 2177 * method, this method does not require NaN {@code sign} 2178 * arguments to be treated as positive values; implementations are 2179 * permitted to treat some NaN arguments as positive and other NaN 2180 * arguments as negative to allow greater performance. 2181 * 2182 * @param magnitude the parameter providing the magnitude of the result 2183 * @param sign the parameter providing the sign of the result 2184 * @return a value with the magnitude of {@code magnitude} 2185 * and the sign of {@code sign}. 2186 * @since 1.6 2187 */ 2188 public static float copySign(float magnitude, float sign) { 2189 return Float.intBitsToFloat((Float.floatToRawIntBits(sign) & 2190 (FloatConsts.SIGN_BIT_MASK)) | 2191 (Float.floatToRawIntBits(magnitude) & 2192 (FloatConsts.EXP_BIT_MASK | 2193 FloatConsts.SIGNIF_BIT_MASK))); 2194 } 2195 2196 /** 2197 * Returns the unbiased exponent used in the representation of a 2198 * {@code float}. Special cases: 2199 * 2200 * <ul> 2201 * <li>If the argument is NaN or infinite, then the result is 2202 * {@link Float#MAX_EXPONENT} + 1. 2203 * <li>If the argument is zero or subnormal, then the result is 2204 * {@link Float#MIN_EXPONENT} -1. 2205 * </ul> 2206 * @param f a {@code float} value 2207 * @return the unbiased exponent of the argument 2208 * @since 1.6 2209 */ 2210 public static int getExponent(float f) { 2211 /* 2212 * Bitwise convert f to integer, mask out exponent bits, shift 2213 * to the right and then subtract out float's bias adjust to 2214 * get true exponent value 2215 */ 2216 return ((Float.floatToRawIntBits(f) & FloatConsts.EXP_BIT_MASK) >> 2217 (FloatConsts.SIGNIFICAND_WIDTH - 1)) - FloatConsts.EXP_BIAS; 2218 } 2219 2220 /** 2221 * Returns the unbiased exponent used in the representation of a 2222 * {@code double}. Special cases: 2223 * 2224 * <ul> 2225 * <li>If the argument is NaN or infinite, then the result is 2226 * {@link Double#MAX_EXPONENT} + 1. 2227 * <li>If the argument is zero or subnormal, then the result is 2228 * {@link Double#MIN_EXPONENT} -1. 2229 * </ul> 2230 * @param d a {@code double} value 2231 * @return the unbiased exponent of the argument 2232 * @since 1.6 2233 */ 2234 public static int getExponent(double d) { 2235 /* 2236 * Bitwise convert d to long, mask out exponent bits, shift 2237 * to the right and then subtract out double's bias adjust to 2238 * get true exponent value. 2239 */ 2240 return (int)(((Double.doubleToRawLongBits(d) & DoubleConsts.EXP_BIT_MASK) >> 2241 (DoubleConsts.SIGNIFICAND_WIDTH - 1)) - DoubleConsts.EXP_BIAS); 2242 } 2243 2244 /** 2245 * Returns the floating-point number adjacent to the first 2246 * argument in the direction of the second argument. If both 2247 * arguments compare as equal the second argument is returned. 2248 * 2249 * <p> 2250 * Special cases: 2251 * <ul> 2252 * <li> If either argument is a NaN, then NaN is returned. 2253 * 2254 * <li> If both arguments are signed zeros, {@code direction} 2255 * is returned unchanged (as implied by the requirement of 2256 * returning the second argument if the arguments compare as 2257 * equal). 2258 * 2259 * <li> If {@code start} is 2260 * ±{@link Double#MIN_VALUE} and {@code direction} 2261 * has a value such that the result should have a smaller 2262 * magnitude, then a zero with the same sign as {@code start} 2263 * is returned. 2264 * 2265 * <li> If {@code start} is infinite and 2266 * {@code direction} has a value such that the result should 2267 * have a smaller magnitude, {@link Double#MAX_VALUE} with the 2268 * same sign as {@code start} is returned. 2269 * 2270 * <li> If {@code start} is equal to ± 2271 * {@link Double#MAX_VALUE} and {@code direction} has a 2272 * value such that the result should have a larger magnitude, an 2273 * infinity with same sign as {@code start} is returned. 2274 * </ul> 2275 * 2276 * @param start starting floating-point value 2277 * @param direction value indicating which of 2278 * {@code start}'s neighbors or {@code start} should 2279 * be returned 2280 * @return The floating-point number adjacent to {@code start} in the 2281 * direction of {@code direction}. 2282 * @since 1.6 2283 */ 2284 public static double nextAfter(double start, double direction) { 2285 /* 2286 * The cases: 2287 * 2288 * nextAfter(+infinity, 0) == MAX_VALUE 2289 * nextAfter(+infinity, +infinity) == +infinity 2290 * nextAfter(-infinity, 0) == -MAX_VALUE 2291 * nextAfter(-infinity, -infinity) == -infinity 2292 * 2293 * are naturally handled without any additional testing 2294 */ 2295 2296 /* 2297 * IEEE 754 floating-point numbers are lexicographically 2298 * ordered if treated as signed-magnitude integers. 2299 * Since Java's integers are two's complement, 2300 * incrementing the two's complement representation of a 2301 * logically negative floating-point value *decrements* 2302 * the signed-magnitude representation. Therefore, when 2303 * the integer representation of a floating-point value 2304 * is negative, the adjustment to the representation is in 2305 * the opposite direction from what would initially be expected. 2306 */ 2307 2308 // Branch to descending case first as it is more costly than ascending 2309 // case due to start != 0.0d conditional. 2310 if (start > direction) { // descending 2311 if (start != 0.0d) { 2312 final long transducer = Double.doubleToRawLongBits(start); 2313 return Double.longBitsToDouble(transducer + ((transducer > 0L) ? -1L : 1L)); 2314 } else { // start == 0.0d && direction < 0.0d 2315 return -Double.MIN_VALUE; 2316 } 2317 } else if (start < direction) { // ascending 2318 // Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0) 2319 // then bitwise convert start to integer. 2320 final long transducer = Double.doubleToRawLongBits(start + 0.0d); 2321 return Double.longBitsToDouble(transducer + ((transducer >= 0L) ? 1L : -1L)); 2322 } else if (start == direction) { 2323 return direction; 2324 } else { // isNaN(start) || isNaN(direction) 2325 return start + direction; 2326 } 2327 } 2328 2329 /** 2330 * Returns the floating-point number adjacent to the first 2331 * argument in the direction of the second argument. If both 2332 * arguments compare as equal a value equivalent to the second argument 2333 * is returned. 2334 * 2335 * <p> 2336 * Special cases: 2337 * <ul> 2338 * <li> If either argument is a NaN, then NaN is returned. 2339 * 2340 * <li> If both arguments are signed zeros, a value equivalent 2341 * to {@code direction} is returned. 2342 * 2343 * <li> If {@code start} is 2344 * ±{@link Float#MIN_VALUE} and {@code direction} 2345 * has a value such that the result should have a smaller 2346 * magnitude, then a zero with the same sign as {@code start} 2347 * is returned. 2348 * 2349 * <li> If {@code start} is infinite and 2350 * {@code direction} has a value such that the result should 2351 * have a smaller magnitude, {@link Float#MAX_VALUE} with the 2352 * same sign as {@code start} is returned. 2353 * 2354 * <li> If {@code start} is equal to ± 2355 * {@link Float#MAX_VALUE} and {@code direction} has a 2356 * value such that the result should have a larger magnitude, an 2357 * infinity with same sign as {@code start} is returned. 2358 * </ul> 2359 * 2360 * @param start starting floating-point value 2361 * @param direction value indicating which of 2362 * {@code start}'s neighbors or {@code start} should 2363 * be returned 2364 * @return The floating-point number adjacent to {@code start} in the 2365 * direction of {@code direction}. 2366 * @since 1.6 2367 */ 2368 public static float nextAfter(float start, double direction) { 2369 /* 2370 * The cases: 2371 * 2372 * nextAfter(+infinity, 0) == MAX_VALUE 2373 * nextAfter(+infinity, +infinity) == +infinity 2374 * nextAfter(-infinity, 0) == -MAX_VALUE 2375 * nextAfter(-infinity, -infinity) == -infinity 2376 * 2377 * are naturally handled without any additional testing 2378 */ 2379 2380 /* 2381 * IEEE 754 floating-point numbers are lexicographically 2382 * ordered if treated as signed-magnitude integers. 2383 * Since Java's integers are two's complement, 2384 * incrementing the two's complement representation of a 2385 * logically negative floating-point value *decrements* 2386 * the signed-magnitude representation. Therefore, when 2387 * the integer representation of a floating-point value 2388 * is negative, the adjustment to the representation is in 2389 * the opposite direction from what would initially be expected. 2390 */ 2391 2392 // Branch to descending case first as it is more costly than ascending 2393 // case due to start != 0.0f conditional. 2394 if (start > direction) { // descending 2395 if (start != 0.0f) { 2396 final int transducer = Float.floatToRawIntBits(start); 2397 return Float.intBitsToFloat(transducer + ((transducer > 0) ? -1 : 1)); 2398 } else { // start == 0.0f && direction < 0.0f 2399 return -Float.MIN_VALUE; 2400 } 2401 } else if (start < direction) { // ascending 2402 // Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0) 2403 // then bitwise convert start to integer. 2404 final int transducer = Float.floatToRawIntBits(start + 0.0f); 2405 return Float.intBitsToFloat(transducer + ((transducer >= 0) ? 1 : -1)); 2406 } else if (start == direction) { 2407 return (float)direction; 2408 } else { // isNaN(start) || isNaN(direction) 2409 return start + (float)direction; 2410 } 2411 } 2412 2413 /** 2414 * Returns the floating-point value adjacent to {@code d} in 2415 * the direction of positive infinity. This method is 2416 * semantically equivalent to {@code nextAfter(d, 2417 * Double.POSITIVE_INFINITY)}; however, a {@code nextUp} 2418 * implementation may run faster than its equivalent 2419 * {@code nextAfter} call. 2420 * 2421 * <p>Special Cases: 2422 * <ul> 2423 * <li> If the argument is NaN, the result is NaN. 2424 * 2425 * <li> If the argument is positive infinity, the result is 2426 * positive infinity. 2427 * 2428 * <li> If the argument is zero, the result is 2429 * {@link Double#MIN_VALUE} 2430 * 2431 * </ul> 2432 * 2433 * @param d starting floating-point value 2434 * @return The adjacent floating-point value closer to positive 2435 * infinity. 2436 * @since 1.6 2437 */ 2438 public static double nextUp(double d) { 2439 // Use a single conditional and handle the likely cases first. 2440 if (d < Double.POSITIVE_INFINITY) { 2441 // Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0). 2442 final long transducer = Double.doubleToRawLongBits(d + 0.0D); 2443 return Double.longBitsToDouble(transducer + ((transducer >= 0L) ? 1L : -1L)); 2444 } else { // d is NaN or +Infinity 2445 return d; 2446 } 2447 } 2448 2449 /** 2450 * Returns the floating-point value adjacent to {@code f} in 2451 * the direction of positive infinity. This method is 2452 * semantically equivalent to {@code nextAfter(f, 2453 * Float.POSITIVE_INFINITY)}; however, a {@code nextUp} 2454 * implementation may run faster than its equivalent 2455 * {@code nextAfter} call. 2456 * 2457 * <p>Special Cases: 2458 * <ul> 2459 * <li> If the argument is NaN, the result is NaN. 2460 * 2461 * <li> If the argument is positive infinity, the result is 2462 * positive infinity. 2463 * 2464 * <li> If the argument is zero, the result is 2465 * {@link Float#MIN_VALUE} 2466 * 2467 * </ul> 2468 * 2469 * @param f starting floating-point value 2470 * @return The adjacent floating-point value closer to positive 2471 * infinity. 2472 * @since 1.6 2473 */ 2474 public static float nextUp(float f) { 2475 // Use a single conditional and handle the likely cases first. 2476 if (f < Float.POSITIVE_INFINITY) { 2477 // Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0). 2478 final int transducer = Float.floatToRawIntBits(f + 0.0F); 2479 return Float.intBitsToFloat(transducer + ((transducer >= 0) ? 1 : -1)); 2480 } else { // f is NaN or +Infinity 2481 return f; 2482 } 2483 } 2484 2485 /** 2486 * Returns the floating-point value adjacent to {@code d} in 2487 * the direction of negative infinity. This method is 2488 * semantically equivalent to {@code nextAfter(d, 2489 * Double.NEGATIVE_INFINITY)}; however, a 2490 * {@code nextDown} implementation may run faster than its 2491 * equivalent {@code nextAfter} call. 2492 * 2493 * <p>Special Cases: 2494 * <ul> 2495 * <li> If the argument is NaN, the result is NaN. 2496 * 2497 * <li> If the argument is negative infinity, the result is 2498 * negative infinity. 2499 * 2500 * <li> If the argument is zero, the result is 2501 * {@code -Double.MIN_VALUE} 2502 * 2503 * </ul> 2504 * 2505 * @param d starting floating-point value 2506 * @return The adjacent floating-point value closer to negative 2507 * infinity. 2508 * @since 1.8 2509 */ 2510 public static double nextDown(double d) { 2511 if (Double.isNaN(d) || d == Double.NEGATIVE_INFINITY) 2512 return d; 2513 else { 2514 if (d == 0.0) 2515 return -Double.MIN_VALUE; 2516 else 2517 return Double.longBitsToDouble(Double.doubleToRawLongBits(d) + 2518 ((d > 0.0d)?-1L:+1L)); 2519 } 2520 } 2521 2522 /** 2523 * Returns the floating-point value adjacent to {@code f} in 2524 * the direction of negative infinity. This method is 2525 * semantically equivalent to {@code nextAfter(f, 2526 * Float.NEGATIVE_INFINITY)}; however, a 2527 * {@code nextDown} implementation may run faster than its 2528 * equivalent {@code nextAfter} call. 2529 * 2530 * <p>Special Cases: 2531 * <ul> 2532 * <li> If the argument is NaN, the result is NaN. 2533 * 2534 * <li> If the argument is negative infinity, the result is 2535 * negative infinity. 2536 * 2537 * <li> If the argument is zero, the result is 2538 * {@code -Float.MIN_VALUE} 2539 * 2540 * </ul> 2541 * 2542 * @param f starting floating-point value 2543 * @return The adjacent floating-point value closer to negative 2544 * infinity. 2545 * @since 1.8 2546 */ 2547 public static float nextDown(float f) { 2548 if (Float.isNaN(f) || f == Float.NEGATIVE_INFINITY) 2549 return f; 2550 else { 2551 if (f == 0.0f) 2552 return -Float.MIN_VALUE; 2553 else 2554 return Float.intBitsToFloat(Float.floatToRawIntBits(f) + 2555 ((f > 0.0f)?-1:+1)); 2556 } 2557 } 2558 2559 /** 2560 * Returns {@code d} × 2561 * 2<sup>{@code scaleFactor}</sup> rounded as if performed 2562 * by a single correctly rounded floating-point multiply to a 2563 * member of the double value set. See the Java 2564 * Language Specification for a discussion of floating-point 2565 * value sets. If the exponent of the result is between {@link 2566 * Double#MIN_EXPONENT} and {@link Double#MAX_EXPONENT}, the 2567 * answer is calculated exactly. If the exponent of the result 2568 * would be larger than {@code Double.MAX_EXPONENT}, an 2569 * infinity is returned. Note that if the result is subnormal, 2570 * precision may be lost; that is, when {@code scalb(x, n)} 2571 * is subnormal, {@code scalb(scalb(x, n), -n)} may not equal 2572 * <i>x</i>. When the result is non-NaN, the result has the same 2573 * sign as {@code d}. 2574 * 2575 * <p>Special cases: 2576 * <ul> 2577 * <li> If the first argument is NaN, NaN is returned. 2578 * <li> If the first argument is infinite, then an infinity of the 2579 * same sign is returned. 2580 * <li> If the first argument is zero, then a zero of the same 2581 * sign is returned. 2582 * </ul> 2583 * 2584 * @param d number to be scaled by a power of two. 2585 * @param scaleFactor power of 2 used to scale {@code d} 2586 * @return {@code d} × 2<sup>{@code scaleFactor}</sup> 2587 * @since 1.6 2588 */ 2589 public static double scalb(double d, int scaleFactor) { 2590 /* 2591 * This method does not need to be declared strictfp to 2592 * compute the same correct result on all platforms. When 2593 * scaling up, it does not matter what order the 2594 * multiply-store operations are done; the result will be 2595 * finite or overflow regardless of the operation ordering. 2596 * However, to get the correct result when scaling down, a 2597 * particular ordering must be used. 2598 * 2599 * When scaling down, the multiply-store operations are 2600 * sequenced so that it is not possible for two consecutive 2601 * multiply-stores to return subnormal results. If one 2602 * multiply-store result is subnormal, the next multiply will 2603 * round it away to zero. This is done by first multiplying 2604 * by 2 ^ (scaleFactor % n) and then multiplying several 2605 * times by 2^n as needed where n is the exponent of number 2606 * that is a covenient power of two. In this way, at most one 2607 * real rounding error occurs. If the double value set is 2608 * being used exclusively, the rounding will occur on a 2609 * multiply. If the double-extended-exponent value set is 2610 * being used, the products will (perhaps) be exact but the 2611 * stores to d are guaranteed to round to the double value 2612 * set. 2613 * 2614 * It is _not_ a valid implementation to first multiply d by 2615 * 2^MIN_EXPONENT and then by 2 ^ (scaleFactor % 2616 * MIN_EXPONENT) since even in a strictfp program double 2617 * rounding on underflow could occur; e.g. if the scaleFactor 2618 * argument was (MIN_EXPONENT - n) and the exponent of d was a 2619 * little less than -(MIN_EXPONENT - n), meaning the final 2620 * result would be subnormal. 2621 * 2622 * Since exact reproducibility of this method can be achieved 2623 * without any undue performance burden, there is no 2624 * compelling reason to allow double rounding on underflow in 2625 * scalb. 2626 */ 2627 2628 // magnitude of a power of two so large that scaling a finite 2629 // nonzero value by it would be guaranteed to over or 2630 // underflow; due to rounding, scaling down takes an 2631 // additional power of two which is reflected here 2632 final int MAX_SCALE = Double.MAX_EXPONENT + -Double.MIN_EXPONENT + 2633 DoubleConsts.SIGNIFICAND_WIDTH + 1; 2634 int exp_adjust = 0; 2635 int scale_increment = 0; 2636 double exp_delta = Double.NaN; 2637 2638 // Make sure scaling factor is in a reasonable range 2639 2640 if(scaleFactor < 0) { 2641 scaleFactor = Math.max(scaleFactor, -MAX_SCALE); 2642 scale_increment = -512; 2643 exp_delta = twoToTheDoubleScaleDown; 2644 } 2645 else { 2646 scaleFactor = Math.min(scaleFactor, MAX_SCALE); 2647 scale_increment = 512; 2648 exp_delta = twoToTheDoubleScaleUp; 2649 } 2650 2651 // Calculate (scaleFactor % +/-512), 512 = 2^9, using 2652 // technique from "Hacker's Delight" section 10-2. 2653 int t = (scaleFactor >> 9-1) >>> 32 - 9; 2654 exp_adjust = ((scaleFactor + t) & (512 -1)) - t; 2655 2656 d *= powerOfTwoD(exp_adjust); 2657 scaleFactor -= exp_adjust; 2658 2659 while(scaleFactor != 0) { 2660 d *= exp_delta; 2661 scaleFactor -= scale_increment; 2662 } 2663 return d; 2664 } 2665 2666 /** 2667 * Returns {@code f} × 2668 * 2<sup>{@code scaleFactor}</sup> rounded as if performed 2669 * by a single correctly rounded floating-point multiply to a 2670 * member of the float value set. See the Java 2671 * Language Specification for a discussion of floating-point 2672 * value sets. If the exponent of the result is between {@link 2673 * Float#MIN_EXPONENT} and {@link Float#MAX_EXPONENT}, the 2674 * answer is calculated exactly. If the exponent of the result 2675 * would be larger than {@code Float.MAX_EXPONENT}, an 2676 * infinity is returned. Note that if the result is subnormal, 2677 * precision may be lost; that is, when {@code scalb(x, n)} 2678 * is subnormal, {@code scalb(scalb(x, n), -n)} may not equal 2679 * <i>x</i>. When the result is non-NaN, the result has the same 2680 * sign as {@code f}. 2681 * 2682 * <p>Special cases: 2683 * <ul> 2684 * <li> If the first argument is NaN, NaN is returned. 2685 * <li> If the first argument is infinite, then an infinity of the 2686 * same sign is returned. 2687 * <li> If the first argument is zero, then a zero of the same 2688 * sign is returned. 2689 * </ul> 2690 * 2691 * @param f number to be scaled by a power of two. 2692 * @param scaleFactor power of 2 used to scale {@code f} 2693 * @return {@code f} × 2<sup>{@code scaleFactor}</sup> 2694 * @since 1.6 2695 */ 2696 public static float scalb(float f, int scaleFactor) { 2697 // magnitude of a power of two so large that scaling a finite 2698 // nonzero value by it would be guaranteed to over or 2699 // underflow; due to rounding, scaling down takes an 2700 // additional power of two which is reflected here 2701 final int MAX_SCALE = Float.MAX_EXPONENT + -Float.MIN_EXPONENT + 2702 FloatConsts.SIGNIFICAND_WIDTH + 1; 2703 2704 // Make sure scaling factor is in a reasonable range 2705 scaleFactor = Math.max(Math.min(scaleFactor, MAX_SCALE), -MAX_SCALE); 2706 2707 /* 2708 * Since + MAX_SCALE for float fits well within the double 2709 * exponent range and + float -> double conversion is exact 2710 * the multiplication below will be exact. Therefore, the 2711 * rounding that occurs when the double product is cast to 2712 * float will be the correctly rounded float result. Since 2713 * all operations other than the final multiply will be exact, 2714 * it is not necessary to declare this method strictfp. 2715 */ 2716 return (float)((double)f*powerOfTwoD(scaleFactor)); 2717 } 2718 2719 // Constants used in scalb 2720 static double twoToTheDoubleScaleUp = powerOfTwoD(512); 2721 static double twoToTheDoubleScaleDown = powerOfTwoD(-512); 2722 2723 /** 2724 * Returns a floating-point power of two in the normal range. 2725 */ 2726 static double powerOfTwoD(int n) { 2727 assert(n >= Double.MIN_EXPONENT && n <= Double.MAX_EXPONENT); 2728 return Double.longBitsToDouble((((long)n + (long)DoubleConsts.EXP_BIAS) << 2729 (DoubleConsts.SIGNIFICAND_WIDTH-1)) 2730 & DoubleConsts.EXP_BIT_MASK); 2731 } 2732 2733 /** 2734 * Returns a floating-point power of two in the normal range. 2735 */ 2736 static float powerOfTwoF(int n) { 2737 assert(n >= Float.MIN_EXPONENT && n <= Float.MAX_EXPONENT); 2738 return Float.intBitsToFloat(((n + FloatConsts.EXP_BIAS) << 2739 (FloatConsts.SIGNIFICAND_WIDTH-1)) 2740 & FloatConsts.EXP_BIT_MASK); 2741 } 2742 }