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/*=========================================================================
*
* Copyright NumFOCUS
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#include "itkMersenneTwisterRandomVariateGenerator.h"
#include "itkTestingMacros.h"
#include <iostream>
int
itkMersenneTwisterRandomVariateGeneratorTest(int, char *[])
{
using Twister = itk::Statistics::MersenneTwisterRandomVariateGenerator;
Twister::IntegerType seed = 1234;
// Test Get/SetSeed
Twister::GetInstance()->SetSeed(seed);
ITK_TEST_SET_GET_VALUE(seed, Twister::GetInstance()->GetSeed());
auto twister = Twister::New();
ITK_EXERCISE_BASIC_OBJECT_METHODS(twister, MersenneTwisterRandomVariateGenerator, RandomVariateGeneratorBase);
// Does the new instance have the same seed?
if (Twister::GetInstance()->GetSeed() + 1 != twister->GetSeed())
{
std::cerr << "New instance does not have the next seed!" << std::endl;
return EXIT_FAILURE;
}
twister->SetSeed(Twister::GetInstance()->GetSeed());
// Check that we get the same series of numbers from the two. Use integers.
for (int i = 0; i < 200; ++i)
{
if (Twister::GetInstance()->GetIntegerVariate() != twister->GetIntegerVariate())
{
std::cerr << "Singleton and new instance deviated at " << i << "th iteration" << std::endl;
return EXIT_FAILURE;
}
}
// Ensure we get the same series of numbers
const Twister::IntegerType expected[5] = { Twister::IntegerType(3294740812u),
Twister::IntegerType(4175194053u),
Twister::IntegerType(3041332341u),
Twister::IntegerType(199851601u),
Twister::IntegerType(3422518480u) };
bool sameSequence = true;
for (const auto i : expected)
{
Twister::IntegerType actual = twister->GetIntegerVariate();
if (actual != i)
{
std::cout << "GetIntegerVariate: expected " << i << " got " << actual << std::endl;
sameSequence = false;
}
}
if (!sameSequence)
{
return EXIT_FAILURE;
}
// Do we get roughly zero mean and unit variance?
// NB: requires a large number of iterations to have variance converge...
double sum = 0.0;
double sum2 = 0.0;
int count = 500000;
for (int i = 0; i < count; ++i)
{
double v = twister->GetNormalVariate();
sum += v;
sum2 += v * v;
}
double mean = sum / static_cast<double>(count);
double variance = sum2 / static_cast<double>(count) - mean * mean;
if (itk::Math::abs(mean) > 0.01)
{
std::cerr << "Mean was " << mean << " expected 0.0 " << std::endl;
return EXIT_FAILURE;
}
if (itk::Math::abs(variance - 1.0) > 0.01)
{
std::cerr << "Variance was " << variance << " expected 1.0 " << std::endl;
return EXIT_FAILURE;
}
twister->Initialize();
twister->SetSeed(1234);
const Twister::IntegerType withSetSeed = twister->GetIntegerVariate();
twister->Initialize(1234);
const Twister::IntegerType withInitialize = twister->GetIntegerVariate();
if (withSetSeed != withInitialize)
{
std::cerr << "Result initializing with SetSeed() did not equal result with Initialize()." << std::endl;
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
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