solidity/tools/yulPhaser/SimulationRNG.cpp
Kamil Śliwak 8f55ead48d yul-phaser: Switch from uint32_t to size_t in SimulationRNG
- Also pass the appriopriate type internally to the distribution instead of relying on the default (which is uint32_t)
2020-06-04 17:19:42 +02:00

66 lines
2.5 KiB
C++

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