lookup.h

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// SPDX-License-Identifier: Apache-2.0
// Copyright Contributors to the OpenQMC Project.
 
 
#pragma once
 
#include "gpu.h"
#include "permute.h"
#include "rotate.h"
 
#include <cassert>
#include <cstdint>
 
namespace oqmc
{
 
OQMC_HOST_DEVICE constexpr std::uint32_t
randomDigitScramble(std::uint32_t value, std::uint32_t hash)
{
    return value ^ hash;
}
 
template <int Table, int Depth>
OQMC_HOST_DEVICE inline void
shuffledScrambledLookup(std::uint32_t index, std::uint32_t hash,
                        const std::uint32_t table[][Table],
                        std::uint32_t sample[Depth])
{
    static_assert(Table >= Depth, "Table size is greater or equal to Depth.");
    static_assert(Depth >= 1, "Pattern depth is greater or equal to one.");
    static_assert(Depth <= 4, "Pattern depth is less or equal to four.");
 
    index = shuffle(index, hash);
 
    for(int i = 0; i < Depth; ++i)
    {
        constexpr auto indexMask = 0xffff;
 
        sample[i] = table[index & indexMask][i];
        sample[i] = randomDigitScramble(sample[i], rotateBytes(hash, i));
    }
}
 
} // namespace oqmc