permute.h

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// SPDX-License-Identifier: Apache-2.0
// Copyright Contributors to the OpenQMC Project.
 
 
#pragma once
 
#include "gpu.h"
#include "reverse.h"
 
#include <cstdint>
 
namespace oqmc
{
 
OQMC_HOST_DEVICE constexpr std::uint32_t
laineKarrasPermutation(std::uint32_t value, std::uint32_t seed)
{
    value ^= value * 0x3d20adea;
    value += seed;
    value *= (seed >> 16) | 1;
    value ^= value * 0x05526c56;
    value ^= value * 0x53a22864;
 
    return value;
}
 
OQMC_HOST_DEVICE constexpr std::uint32_t reverseAndShuffle(std::uint32_t value,
                                                           std::uint32_t seed)
{
    value = reverseBits32(value);
    value = laineKarrasPermutation(value, seed);
 
    return value;
}
 
OQMC_HOST_DEVICE constexpr std::uint32_t shuffle(std::uint32_t value,
                                                 std::uint32_t seed)
{
    value = reverseAndShuffle(value, seed);
    value = reverseBits32(value);
 
    return value;
}
 
} // namespace oqmc