libcruft-util/rand/mwc64x.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2016 Danny Robson <danny@nerdcruft.net>
 */

#ifndef __UTIL_RAND_MWC64X_HPP
#define __UTIL_RAND_MWC64X_HPP

#include <cstdint>

namespace cruft::rand {
    // multiply-with-carry style generator suitable for rapid seeking and
    // GPU generation.
    //
    // as with all such style generators, the seed value is very important.
    // don't allow either half of the uint64_t to be zero.
    struct mwc64x {
    public:
        using value_type = uint32_t;
        using seed_type  = uint64_t;

        explicit mwc64x (seed_type);

        value_type operator() (void);

    private:
        uint64_t m_state;
    };
}


#endif