range.h

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// SPDX-License-Identifier: Apache-2.0
// Copyright Contributors to the OpenQMC Project.
 
 
#pragma once
 
#include "gpu.h"
 
#include <cassert>
#include <cstdint>
 
namespace oqmc
{
 
OQMC_HOST_DEVICE constexpr std::uint32_t uintToRange(std::uint32_t value,
                                                     std::uint32_t range)
{
    assert(range > 0);
 
    // Modern compilers will optimise this down to a standard mult instruction,
    // avoiding 64 bits, taking only the upper order bits in the EAX register.
    const auto x = static_cast<std::uint64_t>(value);
    const auto y = static_cast<std::uint64_t>(range);
    return x * y >> 32;
}
 
OQMC_HOST_DEVICE constexpr std::uint32_t
uintToRange(std::uint32_t value, std::uint32_t begin, std::uint32_t end)
{
    assert(begin < end);
 
    return uintToRange(value, end - begin) + begin;
}
 
} // namespace oqmc