test_StdRandom.cpp

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//////////////////////////////////////////////////////////////////////////////////////
// This file is distributed under the University of Illinois/NCSA Open Source License.
// See LICENSE file in top directory for details.
//
// Copyright (c) 2023 QMCPACK developers.
//
// File developed by: Peter Doak, doakpw@ornl.gov, Oak Ridge National Lab
//                    Steven Hahn, hahnse@ornl.gov, Oak Ridge National lab
//
// File created by: Peter Doak, doakpw@ornl.gov, Oak Ridge National Lab
//////////////////////////////////////////////////////////////////////////////////////


#include "catch.hpp"

#include "Utilities/StdRandom.h"

#include <vector>

namespace qmcplusplus
{

TEST_CASE("StdRandom mt19937 determinism", "[utilities]")
{
  // Verify StdRandom (MT19937 internally) generates a fixed sequence given an fixed initial seed
  // This is not guaranteed by Boost but appears to be the case
  StdRandom<double> our_rng(13);
  std::vector<double> expected = {0.7777024102, 0.6073413305, 0.237541216};
  for (auto i = 0; i < expected.size(); ++i)
    CHECK(our_rng() == Approx(expected[i]));
}

TEST_CASE("StdRandom save and load", "[utilities]")
{
  using DoubleRNG = StdRandom<double>;
  DoubleRNG rng;

  rng.init(111);

  std::vector<double> rng_doubles(100,0.0);
  for(auto& elem : rng_doubles)
    elem = rng();

  std::vector<DoubleRNG::uint_type> state;

  rng.save(state);

  CHECK(state.size() == rng.state_size());

  DoubleRNG rng2;
  rng2.init(110);
  rng2.load(state);

  CHECK(rng2() == rng());
}

TEST_CASE("StdRandom clone", "[utilities]")
{
  using DoubleRNG = StdRandom<double>;
  DoubleRNG rng;

  rng.init(111);
  std::vector<double> rng_doubles(100, 0.0);
  for (auto& elem : rng_doubles)
    elem = rng();

  std::vector<DoubleRNG::uint_type> state1;
  rng.save(state1);

  std::stringstream stream1;
  rng.write(stream1);

  auto rng2 = rng.makeClone();
  std::vector<DoubleRNG::uint_type> state2;
  rng2->save(state2);

  CHECK(state1.size() == state2.size());
  CHECK(state1 == state2);

  std::stringstream stream2;
  rng2->write(stream2);

  CHECK(stream1.str() == stream2.str());

  CHECK((*rng2)() == rng());
  CHECK((*rng2)() == rng());
}

} // namespace qmcplusplus