1 /*
2 * Copyright (c) 2015, 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 #ifndef SHARE_VM_GC_G1_G1PREDICTIONS_HPP
26 #define SHARE_VM_GC_G1_G1PREDICTIONS_HPP
27
28 #include "utilities/numberSeq.hpp"
29
30 // Utility class containing various helper methods for prediction.
31 class G1Predictions VALUE_OBJ_CLASS_SPEC {
32 private:
33 double _sigma;
34
35 // This function is used to estimate the stddev of sample sets. There is some
36 // special consideration of small sample sets: the actual stddev for them is
37 // not very useful, so we calculate some value based on the sample average.
38 // Five or more samples yields zero (at that point we use the stddev); fewer
39 // scale the sample set average linearly from two times the average to 0.5 times
40 // it.
41 double stddev_estimate(TruncatedSeq const* seq) const {
42 double estimate = seq->dsd();
43 int const samples = seq->num();
44 if (samples < 5) {
45 estimate = MAX2(seq->davg() * (5 - samples) / 2.0, estimate);
46 }
47 return estimate;
48 }
49 public:
50 G1Predictions(double sigma) : _sigma(sigma) {
51 assert(sigma >= 0.0, "Confidence must be larger than or equal to zero");
52 }
53
54 // Confidence factor.
55 double sigma() const { return _sigma; }
56
57 double get_new_prediction(TruncatedSeq const* seq) const {
58 return seq->davg() + _sigma * stddev_estimate(seq);
59 }
60
61 #ifndef PRODUCT
62 static void test();
63 #endif
64 };
65
66 #endif // SHARE_VM_GC_G1_G1PREDICTIONS_HPP
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1 /*
2 * Copyright (c) 2015, 2016, 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 #ifndef SHARE_VM_GC_G1_G1PREDICTIONS_HPP
25 #define SHARE_VM_GC_G1_G1PREDICTIONS_HPP
26
27 #include "utilities/numberSeq.hpp"
28
29 // Utility class containing various helper methods for prediction.
30 class G1Predictions VALUE_OBJ_CLASS_SPEC {
31 private:
32 double _sigma;
33
34 // This function is used to estimate the stddev of sample sets. There is some
35 // special consideration of small sample sets: the actual stddev for them is
36 // not very useful, so we calculate some value based on the sample average.
37 // Five or more samples yields zero (at that point we use the stddev); fewer
38 // scale the sample set average linearly from two times the average to 0.5 times
39 // it.
40 double stddev_estimate(TruncatedSeq const* seq) const {
41 double estimate = seq->dsd();
42 int const samples = seq->num();
43 if (samples < 5) {
44 estimate = MAX2(seq->davg() * (5 - samples) / 2.0, estimate);
45 }
46 return estimate;
47 }
48 public:
49 G1Predictions(double sigma) : _sigma(sigma) {
50 assert(sigma >= 0.0, "Confidence must be larger than or equal to zero");
51 }
52
53 // Confidence factor.
54 double sigma() const { return _sigma; }
55
56 double get_new_prediction(TruncatedSeq const* seq) const {
57 return seq->davg() + _sigma * stddev_estimate(seq);
58 }
59 };
60
61 #endif // SHARE_VM_GC_G1_G1PREDICTIONS_HPP
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