1 /*
   2  * Copyright (c) 2016, 2017, 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.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /*
  25  * @test
  26  * @library /test/lib
  27  * @run main MultiplicationTests
  28  * @bug 5100935
  29  * @summary Tests for multiplication methods (use -Dseed=X to set PRNG seed)
  30  * @key randomness
  31  */
  32 
  33 import java.math.BigInteger;
  34 import jdk.test.lib.RandomFactory;
  35 
  36 public class MultiplicationTests {
  37     private MultiplicationTests(){}
  38 
  39     // Number of random products to test.
  40     private static final int COUNT = 1 << 16;
  41 
  42     // Initialize shared random number generator
  43     private static java.util.Random rnd = RandomFactory.getRandom();
  44 
  45     // Calculate high 64 bits of 128 product using BigInteger.
  46     private static long multiplyHighBigInt(long x, long y) {
  47         return BigInteger.valueOf(x).multiply(BigInteger.valueOf(y))
  48             .shiftRight(64).longValue();
  49     }
  50 
  51     // Check Math.multiplyHigh(x,y) against multiplyHighBigInt(x,y)
  52     private static boolean check(long x, long y) {
  53         long p1 = multiplyHighBigInt(x, y);
  54         long p2 = Math.multiplyHigh(x, y);
  55         if (p1 != p2) {
  56             System.err.printf("Error - x:%d y:%d p1:%d p2:%d\n", x, y, p1, p2);
  57             return false;
  58         } else {
  59             return true;
  60         }
  61     }
  62 
  63     private static int testMultiplyHigh() {
  64         int failures = 0;
  65 
  66         // check some boundary cases
  67         long[][] v = new long[][]{
  68             {0L, 0L},
  69             {-1L, 0L},
  70             {0L, -1L},
  71             {1L, 0L},
  72             {0L, 1L},
  73             {-1L, -1L},
  74             {-1L, 1L},
  75             {1L, -1L},
  76             {1L, 1L},
  77             {Long.MAX_VALUE, Long.MAX_VALUE},
  78             {Long.MAX_VALUE, -Long.MAX_VALUE},
  79             {-Long.MAX_VALUE, Long.MAX_VALUE},
  80             {Long.MAX_VALUE, Long.MIN_VALUE},
  81             {Long.MIN_VALUE, Long.MAX_VALUE},
  82             {Long.MIN_VALUE, Long.MIN_VALUE}
  83         };
  84 
  85         for (long[] xy : v) {
  86             if(!check(xy[0], xy[1])) {
  87                 failures++;
  88             }
  89         }
  90 
  91         // check some random values
  92         for (int i = 0; i < COUNT; i++) {
  93             if (!check(rnd.nextLong(), rnd.nextLong())) {
  94                 failures++;
  95             }
  96         }
  97 
  98         return failures;
  99     }
 100 
 101     public static void main(String argv[]) {
 102         int failures = testMultiplyHigh();
 103 
 104         if (failures > 0) {
 105             System.err.println("Multiplication testing encountered "
 106                                + failures + " failures.");
 107             throw new RuntimeException();
 108         } else {
 109             System.out.println("MultiplicationTests succeeded");
 110         }
 111     }
 112 }