src/gromacs/random/tests/exponentialdistribution.cpp

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  35 /*! \internal \file
  36  * \brief Tests for GROMACS exponential distribution
  37  *
  38  * \author Erik Lindahl <erik.lindahl@gmail.com>
  39  * \ingroup module_random
  40  */
  41 #include "gmxpre.h"
  42
  43 #include "gromacs/random/exponentialdistribution.h"
  44
  45 #include <gtest/gtest.h>
  46
  47 #include "gromacs/random/threefry.h"
  48
  49 #include "testutils/refdata.h"
  50 #include "testutils/testasserts.h"
  51
  52 namespace gmx
  53 {
  54
  55 namespace
  56 {
  57
  58 TEST(ExponentialDistributionTest, Output)
  59 {
  60     gmx::test::TestReferenceData        data;
  61     gmx::test::TestReferenceChecker     checker(data.rootChecker());
  62
  63     gmx::ThreeFry2x64<8>                rng(123456, gmx::RandomDomain::Other);
  64     gmx::ExponentialDistribution<real>  dist(5.0);
  65     std::vector<real>                   result;
  66
  67     for (int i = 0; i < 10; i++)
  68     {
  69         result.push_back(dist(rng));
  70     }
  71
  72     // The implementation of the exponential distribution both in GROMACS and all current C++
  73     // standard libraries tested is fragile since it computes an intermediate value by subtracting
  74     // a random number in [0,1) from 1.0. This should not affect the accuracy of the final distribution,
  75     // but depending on the compiler optimization individual values will show a somewhat larger
  76     // fluctuation compared to the other distributions.
  77     checker.setDefaultTolerance(gmx::test::relativeToleranceAsFloatingPoint(1.0, 1e-6));
  78     checker.checkSequence(result.begin(), result.end(), "ExponentialDistribution");
  79 }
  80
  81
  82 TEST(ExponentialDistributionTest, Logical)
  83 {
  84     gmx::ThreeFry2x64<8>                rng(123456, gmx::RandomDomain::Other);
  85     gmx::ExponentialDistribution<real>  distA(2.0);
  86     gmx::ExponentialDistribution<real>  distB(2.0);
  87     gmx::ExponentialDistribution<real>  distC(3.0);
  88
  89     EXPECT_EQ(distA, distB);
  90     EXPECT_NE(distA, distC);
  91 }
  92
  93
  94 TEST(ExponentialDistributionTest, Reset)
  95 {
  96     gmx::ThreeFry2x64<8>                                rng(123456, gmx::RandomDomain::Other);
  97     gmx::ExponentialDistribution<real>                  distA(2.0);
  98     gmx::ExponentialDistribution<real>                  distB(2.0);
  99     gmx::ExponentialDistribution<>::result_type         valA, valB;
 100
 101     valA = distA(rng);
 102
 103     distB(rng);
 104     rng.restart();
 105     distB.reset();
 106
 107     valB = distB(rng);
 108
 109     EXPECT_REAL_EQ_TOL(valA, valB, gmx::test::ulpTolerance(0));
 110 }
 111
 112 TEST(ExponentialDistributionTest, AltParam)
 113 {
 114     gmx::ThreeFry2x64<8>                            rngA(123456, gmx::RandomDomain::Other);
 115     gmx::ThreeFry2x64<8>                            rngB(123456, gmx::RandomDomain::Other);
 116     gmx::ExponentialDistribution<real>              distA(2.0);
 117     gmx::ExponentialDistribution<real>              distB; // default parameters
 118     gmx::ExponentialDistribution<real>::param_type  paramA(2.0);
 119
 120     EXPECT_NE(distA(rngA), distB(rngB));
 121     rngA.restart();
 122     rngB.restart();
 123     distA.reset();
 124     distB.reset();
 125     EXPECT_REAL_EQ_TOL(distA(rngA), distB(rngB, paramA), gmx::test::ulpTolerance(0));
 126 }
 127
 128 }      // namespace anonymous
 129
 130 }      // namespace gmx