rank1.h

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// SPDX-License-Identifier: Apache-2.0
// Copyright Contributors to the OpenQMC Project.
 
 
#pragma once
 
#include "gpu.h"
#include "pcg.h"
#include "permute.h"
 
#include <cassert>
#include <cstdint>
 
namespace oqmc
{
 
OQMC_HOST_DEVICE constexpr std::uint32_t rotate(std::uint32_t value,
                                                std::uint32_t distance)
{
    return value + distance;
}
 
OQMC_HOST_DEVICE constexpr std::uint32_t
latticeReversedIndex(std::uint32_t index, int dimension)
{
    assert(dimension >= 0);
    assert(dimension <= 3);
 
    // Following Rank1 lattice numbers were taken from the orignal publication
    // listed at the top of this file.
 
    // clang-format off
    constexpr int lattice[4] = {
        1,
        364981,
        245389,
        97823,
    };
    // clang-format on
 
    return lattice[dimension] * index;
}
 
template <int Depth>
OQMC_HOST_DEVICE constexpr void
shuffledRotatedLattice(std::uint32_t index, std::uint32_t patternId,
                       std::uint32_t sample[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 = reverseAndShuffle(index, pcg::output(patternId));
 
    for(int i = 0; i < Depth; ++i)
    {
        sample[i] = latticeReversedIndex(index, i);
        sample[i] = rotate(sample[i], pcg::rng(patternId));
    }
}
 
} // namespace oqmc