MersenneTwister.cpp

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
//------------------------------------------------------------------------------
// Includes
//------------------------------------------------------------------------------
#include "MantidKernel/MersenneTwister.h"
 
#include "MantidKernel/uniform_int_distribution.h"
 
#include <Poco/Timestamp.h>
 
namespace Mantid::Kernel {
 
//------------------------------------------------------------------------------
// Public member functions
//------------------------------------------------------------------------------
 
MersenneTwister::MersenneTwister(const size_t seedValue) : MersenneTwister(seedValue, 0.0, 1.0) {}
 
MersenneTwister::MersenneTwister() : MersenneTwister(0.0, 1.0) {}
 
MersenneTwister::MersenneTwister(const double start, const double end)
    : MersenneTwister(Poco::Timestamp().epochMicroseconds(), start, end) {}
 
MersenneTwister::MersenneTwister(const size_t seedValue, const double start, const double end)
    : m_engine(), uniformRealDistribution(start, end), m_start(start), m_end(end), m_seed(), m_savedEngine() {
  setSeed(seedValue);
}
 
void MersenneTwister::setSeed(const size_t seedValue) {
  m_seed = static_cast<std::mt19937::result_type>(seedValue);
  m_engine.seed(m_seed);
  m_savedEngine = std::make_unique<std::mt19937>(m_engine);
}
 
void MersenneTwister::setRange(const double start, const double end) {
  m_start = start;
  m_end = end;
  uniformRealDistribution = std::uniform_real_distribution<double>(start, end);
}
 
int MersenneTwister::nextInt(int start, int end) {
  return Mantid::Kernel::uniform_int_distribution<int>(start, end)(m_engine);
}
 
void MersenneTwister::restart() { setSeed(m_seed); }
 
void MersenneTwister::save() { m_savedEngine = std::make_unique<std::mt19937>(m_engine); }
 
void MersenneTwister::restore() {
  // Copy saved to current, still distinct objects so that another restore still
  // brings us
  // back to the originally saved point
  if (m_savedEngine) {
    m_engine = std::mt19937(*m_savedEngine);
  } else {
    restart();
  }
}
} // namespace Mantid::Kernel