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//===-- flang/unittests/RuntimeGTest/Random.cpp -----------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "flang/Runtime//random.h"
#include "gtest/gtest.h"
#include "flang/Runtime/descriptor.h"
#include "flang/Runtime/type-code.h"
#include <cmath>
using namespace Fortran::runtime;
TEST(RandomNumber, Real4) {
StaticDescriptor<1> statDesc;
Descriptor &harvest{statDesc.descriptor()};
static constexpr int n{10000};
float xs[n]{};
SubscriptValue extent[1]{n};
harvest.Establish(TypeCategory::Real, 4, xs, 1, extent);
RTNAME(RandomNumber)(harvest, __FILE__, __LINE__);
double sum{0};
for (int j{0}; j < n; ++j) {
sum += xs[j];
}
double mean{sum / n};
std::fprintf(stderr, "mean of %d random numbers: %g\n", n, mean);
EXPECT_GE(mean, 0.95 * 0.5); // mean of uniform dist [0..1] is of course 0.5
EXPECT_LE(mean, 1.05 * 0.5);
double sumsq{0};
for (int j{0}; j < n; ++j) {
double diff{xs[j] - mean};
sumsq += diff * diff;
}
double sdev{std::sqrt(sumsq / n)};
std::fprintf(stderr, "stddev of %d random numbers: %g\n", n, sdev);
double expect{1.0 / std::sqrt(12.0)}; // stddev of uniform dist [0..1]
EXPECT_GE(sdev, 0.95 * expect);
EXPECT_LT(sdev, 1.05 * expect);
}
TEST(RandomNumber, RandomSeed) {
StaticDescriptor<1> statDesc[2];
Descriptor &desc{statDesc[0].descriptor()};
std::int32_t n;
desc.Establish(TypeCategory::Integer, 4, &n, 0, nullptr);
RTNAME(RandomSeedSize)(desc, __FILE__, __LINE__);
EXPECT_EQ(n, 1);
SubscriptValue extent[1]{1};
desc.Establish(TypeCategory::Integer, 4, &n, 1, extent);
RTNAME(RandomSeedGet)(desc, __FILE__, __LINE__);
Descriptor &harvest{statDesc[1].descriptor()};
float x;
harvest.Establish(TypeCategory::Real, 4, &x, 1, extent);
RTNAME(RandomNumber)(harvest, __FILE__, __LINE__);
float got{x};
RTNAME(RandomSeedPut)(desc, __FILE__, __LINE__); // n from RandomSeedGet()
RTNAME(RandomNumber)(harvest, __FILE__, __LINE__);
EXPECT_EQ(x, got);
}