71 lines
2.5 KiB
C++
71 lines
2.5 KiB
C++
/*
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* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_GC_G1_G1PREDICTIONS_HPP
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#define SHARE_GC_G1_G1PREDICTIONS_HPP
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#include "utilities/numberSeq.hpp"
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// Utility class containing various helper methods for prediction.
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class G1Predictions {
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private:
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double _sigma;
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// This function is used to estimate the stddev of sample sets. There is some
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// special consideration of small sample sets: the actual stddev for them is
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// not very useful, so we calculate some value based on the sample average.
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// Five or more samples yields zero (at that point we use the stddev); fewer
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// scale the sample set average linearly from two times the average to 0.5 times
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// it.
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double stddev_estimate(TruncatedSeq const* seq) const {
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double estimate = seq->dsd();
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int const samples = seq->num();
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if (samples < 5) {
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estimate = MAX2(seq->davg() * (5 - samples) / 2.0, estimate);
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}
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return estimate;
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}
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public:
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G1Predictions(double sigma) : _sigma(sigma) {
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assert(sigma >= 0.0, "Confidence must be larger than or equal to zero");
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}
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// Confidence factor.
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double sigma() const { return _sigma; }
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double predict(TruncatedSeq const* seq) const {
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return seq->davg() + _sigma * stddev_estimate(seq);
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}
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double predict_in_unit_interval(TruncatedSeq const* seq) const {
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return clamp(predict(seq), 0.0, 1.0);
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}
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double predict_zero_bounded(TruncatedSeq const* seq) const {
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return MAX2(predict(seq), 0.0);
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}
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};
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#endif // SHARE_GC_G1_G1PREDICTIONS_HPP
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