mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
67 lines
2.5 KiB
C++
67 lines
2.5 KiB
C++
/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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// SPDX-License-Identifier: GPL-3.0
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#include <tools/yulPhaser/SimulationRNG.h>
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// NOTE: The code would work with std::random but the results for a given seed would not be reproducible
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// across different STL implementations. Boost does not guarantee this either but at least it has only one
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// implementation. Reproducibility is not a hard requirement for yul-phaser but it's nice to have.
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#include <boost/random/bernoulli_distribution.hpp>
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#include <boost/random/binomial_distribution.hpp>
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#include <boost/random/uniform_int_distribution.hpp>
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#include <ctime>
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#include <limits>
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using namespace std;
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using namespace solidity;
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using namespace solidity::phaser;
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thread_local boost::random::mt19937 SimulationRNG::s_generator(SimulationRNG::generateSeed());
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bool SimulationRNG::bernoulliTrial(double _successProbability)
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{
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boost::random::bernoulli_distribution<double> distribution(_successProbability);
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return distribution(s_generator);
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}
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size_t SimulationRNG::uniformInt(size_t _min, size_t _max)
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{
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boost::random::uniform_int_distribution<size_t> distribution(_min, _max);
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return distribution(s_generator);
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}
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size_t SimulationRNG::binomialInt(size_t _numTrials, double _successProbability)
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{
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// NOTE: binomial_distribution<size_t> would not work because it internally tries to use abs()
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// and fails to compile due to ambiguous conversion.
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assert(_numTrials <= static_cast<size_t>(numeric_limits<long>::max()));
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boost::random::binomial_distribution<long> distribution(static_cast<long>(_numTrials), _successProbability);
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return static_cast<size_t>(distribution(s_generator));
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}
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uint32_t SimulationRNG::generateSeed()
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{
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// This is not a secure way to seed the generator but it's good enough for simulation purposes.
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// The only thing that matters for us is that the sequence is different on each run and that
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// it fits the expected distribution. It does not have to be 100% unpredictable.
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return time(nullptr);
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}
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