flang/unittests/Runtime/Random.cpp

   1 //===-- flang/unittests/Runtime/Random.cpp ----------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "flang/Runtime//random.h"
  10 #include "gtest/gtest.h"
  11 #include "flang/Runtime/descriptor.h"
  12 #include "flang/Runtime/type-code.h"
  13 #include <cmath>
  14
  15 using namespace Fortran::runtime;
  16
  17 TEST(RandomNumber, Real4) {
  18   StaticDescriptor<1> statDesc;
  19   Descriptor &harvest{statDesc.descriptor()};
  20   static constexpr int n{10000};
  21   float xs[n]{};
  22   SubscriptValue extent[1]{n};
  23   harvest.Establish(TypeCategory::Real, 4, xs, 1, extent);
  24   RTNAME(RandomNumber)(harvest, __FILE__, __LINE__);
  25   double sum{0};
  26   for (int j{0}; j < n; ++j) {
  27     sum += xs[j];
  28   }
  29   double mean{sum / n};
  30   std::fprintf(stderr, "mean of %d random numbers: %g\n", n, mean);
  31   EXPECT_GE(mean, 0.95 * 0.5); // mean of uniform dist [0..1] is of course 0.5
  32   EXPECT_LE(mean, 1.05 * 0.5);
  33   double sumsq{0};
  34   for (int j{0}; j < n; ++j) {
  35     double diff{xs[j] - mean};
  36     sumsq += diff * diff;
  37   }
  38   double sdev{std::sqrt(sumsq / n)};
  39   std::fprintf(stderr, "stddev of %d random numbers: %g\n", n, sdev);
  40   double expect{1.0 / std::sqrt(12.0)}; // stddev of uniform dist [0..1]
  41   EXPECT_GE(sdev, 0.95 * expect);
  42   EXPECT_LT(sdev, 1.05 * expect);
  43 }
  44
  45 TEST(RandomNumber, RandomSeed) {
  46   StaticDescriptor<1> statDesc[2];
  47   Descriptor &desc{statDesc[0].descriptor()};
  48   std::int32_t n;
  49   desc.Establish(TypeCategory::Integer, 4, &n, 0, nullptr);
  50   RTNAME(RandomSeedSize)(&desc, __FILE__, __LINE__);
  51   EXPECT_EQ(n, 1);
  52   SubscriptValue extent[1]{1};
  53   desc.Establish(TypeCategory::Integer, 4, &n, 1, extent);
  54   RTNAME(RandomSeedGet)(&desc, __FILE__, __LINE__);
  55   Descriptor &harvest{statDesc[1].descriptor()};
  56   float x;
  57   harvest.Establish(TypeCategory::Real, 4, &x, 1, extent);
  58   RTNAME(RandomNumber)(harvest, __FILE__, __LINE__);
  59   float got{x};
  60   RTNAME(RandomSeedPut)(&desc, __FILE__, __LINE__); // n from RandomSeedGet()
  61   RTNAME(RandomNumber)(harvest, __FILE__, __LINE__);
  62   EXPECT_EQ(x, got);
  63 }