rdrand.hpp

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//============================================================================
// vSMC/include/vsmc/rng/rdrand.hpp
//----------------------------------------------------------------------------
//                         vSMC: Scalable Monte Carlo
//----------------------------------------------------------------------------
// Copyright (c) 2013,2014, Yan Zhou
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//   Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
//   Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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//============================================================================

#ifndef VSMC_RNG_RDRAND_HPP
#define VSMC_RNG_RDRAND_HPP

#include <vsmc/rng/internal/common.hpp>
#include <vsmc/rng/generator_wrapper.hpp>
#include <immintrin.h>

#ifndef VSMC_RDRAND_NTRIAL_MAX
#define VSMC_RDRAND_NTRIAL_MAX 10
#endif

#define VSMC_STATIC_ASSERT_RNG_RDRAND_GENERATOR_RESULT_TYPE(ResultType) \
    VSMC_STATIC_ASSERT((                                                     \
                cxx11::is_same<ResultType, uint16_t>::value ||               \
                cxx11::is_same<ResultType, uint32_t>::value ||               \
                cxx11::is_same<ResultType, uint64_t>::value),                \
            USE_RDRANDGenerator_WITH_RESULT_TYPE_OTHER_THAN_uint16_t_OR_uint32_t_OR_uint64_t)

#define VSMC_STATIC_ASSERT_RNG_RDRAND_GENERATOR \
    VSMC_STATIC_ASSERT_RNG_RDRAND_GENERATOR_RESULT_TYPE(ResultType);

#define VSMC_RUNTIME_WARNING_RNG_RDRAND_GENERATOR_NTRIAL(ntrial, NTrialMax) \
    VSMC_RUNTIME_WARNING((ntrial < NTrialMax),                                \
            ("**RDRAND::generate** MAXIMUM NUMBER OF TRIALS EXCEEDED"))

namespace vsmc {

template <typename UIntType> inline bool rdrand (UIntType *);

template <> inline bool rdrand<uint16_t> (uint16_t *rand)
{
    unsigned short r;
    int cf = _rdrand16_step(&r);
    *rand = static_cast<uint16_t>(r);

    return cf != 0;
}

template <> inline bool rdrand<uint32_t> (uint32_t *rand)
{
    unsigned r;
    int cf = _rdrand32_step(&r);
    *rand = static_cast<uint32_t>(r);

    return cf != 0;
}

template <> inline bool rdrand<uint64_t> (uint64_t *rand)
{
    unsigned VSMC_INT64 r;
    int cf = _rdrand64_step(&r);
    *rand = static_cast<uint64_t>(r);

    return cf != 0;
}

template <typename ResultType, std::size_t NTrialMax = VSMC_RDRAND_NTRIAL_MAX>
class RDRANDGenerator
{
    public :

    typedef ResultType result_type;

    static result_type generate ()
    {
        VSMC_STATIC_ASSERT_RNG_RDRAND_GENERATOR;

        result_type r;
        std::size_t ntrial = 0;
        while (!rdrand<result_type>(&r) && ntrial != NTrialMax)
            ++ntrial;
        VSMC_RUNTIME_WARNING_RNG_RDRAND_GENERATOR_NTRIAL(ntrial, NTrialMax);

        return r;
    }
}; // class RDRANDGenertor

typedef GeneratorWrapper<uint16_t, RDRANDGenerator<uint16_t> > RDRAND16;

typedef GeneratorWrapper<uint32_t, RDRANDGenerator<uint32_t> > RDRAND32;

typedef GeneratorWrapper<uint64_t, RDRANDGenerator<uint64_t> > RDRAND64;

} // namespace vsmc

#endif//  VSMC_RNG_RDRAND_HPP