openqmc/src/tests/pcg.cpp at main · AcademySoftwareFoundation/openqmc · GitHub

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// SPDX-License-Identifier: Apache-2.0
// Copyright Contributors to the OpenQMC Project.

#include "hypothesis.h"
#include <oqmc/pcg.h>
#include <oqmc/unused.h>

#include <gtest/gtest.h>

#include <array>
#include <cstdint>

namespace
{

struct SamplerV1
{
	void initialise(int seed)
	{
		state = oqmc::pcg::init(seed);
	}

	void sample(int index, std::uint32_t out[2])
	{
		OQMC_MAYBE_UNUSED(index);

		out[0] = oqmc::pcg::rng(state);
		out[1] = oqmc::pcg::rng(state);
	}

	std::uint32_t state;
};

struct SamplerV2
{
	void initialise(int seed)
	{
		hash = oqmc::pcg::hash(seed);
	}

	void sample(int index, std::uint32_t out[2]) const
	{
		out[0] = oqmc::pcg::hash(hash + index * 2 + 0);
		out[1] = oqmc::pcg::hash(hash + index * 2 + 1);
	}

	std::uint32_t hash;
};

ALL_HYPOTHESIS_TESTS(PcgTest, Sequential, (SamplerV1()))
ALL_HYPOTHESIS_TESTS(PcgTest, Parallel, (SamplerV2()))

constexpr std::array<std::uint32_t, 20> primes{
    2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71,
};

constexpr std::array<std::uint32_t, 10> powers{
    1, 2, 4, 8, 16, 32, 64, 128, 256, 512,
};

TEST(PcgTest, StateTransitionChange)
{
	EXPECT_NE(oqmc::pcg::stateTransition(0), 0);

	for(const auto input : primes)
	{
		EXPECT_NE(oqmc::pcg::stateTransition(input), input);
	}
}

TEST(PcgTest, OutputPermutation)
{
	EXPECT_EQ(oqmc::pcg::output(0), 0);

	for(const auto input : primes)
	{
		EXPECT_NE(oqmc::pcg::output(input), input);
	}
}

TEST(PcgTest, StateTransitionOutputNotEqual)
{
	EXPECT_NE(oqmc::pcg::stateTransition(0), oqmc::pcg::output(0));

	for(auto input : primes)
	{
		EXPECT_NE(oqmc::pcg::stateTransition(input), oqmc::pcg::output(input));
	}
}

TEST(PcgTest, InitStateDefault)
{
	EXPECT_EQ(oqmc::pcg::init(), oqmc::pcg::init(0));
}

TEST(PcgTest, InitStateNonEqual)
{
	const auto zeroState = oqmc::pcg::init();

	auto lastState = zeroState;
	for(auto seed : primes)
	{
		const auto primeState = oqmc::pcg::init(seed);

		EXPECT_NE(zeroState, primeState);
		EXPECT_NE(lastState, primeState);

		lastState = primeState;
	}

	lastState = zeroState;
	for(auto seed : powers)
	{
		const auto powerState = oqmc::pcg::init(seed);

		EXPECT_NE(zeroState, powerState);
		EXPECT_NE(lastState, powerState);

		lastState = powerState;
	}
}

TEST(PcgTest, HashNonMutatingState)
{
	for(auto before : primes)
	{
		auto key = before;
		oqmc::pcg::hash(key);

		EXPECT_EQ(before, key);
	}
}

TEST(PcgTest, RngMutatingState)
{
	for(auto before : primes)
	{
		auto state = before;
		oqmc::pcg::rng(state);

		EXPECT_NE(before, state);
	}
}

TEST(PcgTest, HashRngEqual)
{
	for(auto seed : primes)
	{
		auto state = oqmc::pcg::init(seed);

		const auto hash = oqmc::pcg::hash(state);
		const auto rnd = oqmc::pcg::rng(state);

		EXPECT_EQ(hash, rnd);
	}
}

} // namespace