seed.hpp

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//============================================================================
// vSMC/include/vsmc/rng/seed.hpp
//----------------------------------------------------------------------------
//                         vSMC: Scalable Monte Carlo
//----------------------------------------------------------------------------
// Copyright (c) 2013-2016, 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
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//============================================================================

#ifndef VSMC_RNG_SEED_HPP
#define VSMC_RNG_SEED_HPP

#include <vsmc/rng/internal/common.hpp>
#include <vsmc/rng/counter.hpp>

#define VSMC_RUNTIME_ASSERT_RNG_SEED_GENERATOR_MODULO(div, rem)               \
    VSMC_RUNTIME_ASSERT((div > rem),                                          \
        "**SeedGenerator::modulo** "                                          \
        "REMAINDER IS NOT SMALLER THAN THE DIVISOR")

#define VSMC_RUNTIME_WARNING_RNG_SEED_GENERATOR_MODULO(div, rem)              \
    VSMC_RUNTIME_WARNING((div == 1 && rem == 0),                              \
        "**SeedGenerator::modulo** "                                          \
        "COUNTER TYPE SEED DOES NOT SUPPORT MODULO")

#define VSMC_RUNTIME_ASSERT_RNG_SEED_MAX(seed_max)                            \
    VSMC_RUNTIME_ASSERT((seed_max > 1),                                       \
        "**SeedGenerator::modulo** "                                          \
        "THE MAXIMUM OF THE INTERNAL SEED IS NO LARGER THAN 1")

#ifndef VSMC_SEED_RESULT_TYPE
#define VSMC_SEED_RESULT_TYPE unsigned
#endif

namespace vsmc
{

template <typename ID, typename ResultType = VSMC_SEED_RESULT_TYPE>
class SeedGenerator
{
    static_assert(std::is_unsigned<ResultType>::value,
        "**SeedGenerator** USED WITH ResultType OTHER THAN UNSIGEND INTEGER "
        "TYPES");

    public:
    using result_type = ResultType;
    using skip_type = ResultType;

    SeedGenerator(const SeedGenerator<ID, ResultType> &) = delete;

    SeedGenerator<ID, ResultType> &operator=(
        const SeedGenerator<ID, ResultType> &) = delete;

    static SeedGenerator<ID, ResultType> &instance()
    {
        static SeedGenerator<ID, ResultType> seed;

        return seed;
    }

    template <typename RNGType>
    void seed_rng(RNGType &rng)
    {
        rng.seed(get());
    }

    result_type get()
    {
        skip();

        return seed_ * divisor_ + remainder_;
    }

    result_type get_scalar() { return get(); }

    void set(result_type seed) { seed_ = seed % seed_max_; }

    result_type seed() const { return seed_; }

    result_type seed_max() const { return seed_max_; }

    skip_type divisor() const { return divisor_; }

    skip_type remainder() const { return remainder_; }

    void modulo(skip_type div, skip_type rem)
    {
        VSMC_RUNTIME_ASSERT_RNG_SEED_GENERATOR_MODULO(div, rem);

        divisor_ = div;
        remainder_ = rem;
        seed_max_ = std::numeric_limits<skip_type>::max();
        seed_max_ -= seed_max_ % divisor_;
        seed_max_ /= divisor_;

        VSMC_RUNTIME_ASSERT_RNG_SEED_MAX(seed_max_);

        set(seed_);
    }

    void skip(skip_type steps)
    {
        result_type incr = steps % seed_max_;
        result_type diff = seed_max_ - seed_;
        seed_ = incr <= diff ? (seed_ + incr) : (incr - diff);
    }

    void skip()
    {
        if (seed_ < seed_max_)
            ++seed_;
        else
            seed_ = 1;
    }

    template <typename CharT, typename Traits>
    friend std::basic_ostream<CharT, Traits> &operator<<(
        std::basic_ostream<CharT, Traits> &os,
        const SeedGenerator<ID, ResultType> &sg)
    {
        if (!os.good())
            return os;

        os << sg.seed_ << ' ';
        os << sg.divisor_ << ' ';
        os << sg.remainder_;

        return os;
    }

    template <typename CharT, typename Traits>
    friend std::basic_istream<CharT, Traits> &operator>>(
        std::basic_istream<CharT, Traits> &is,
        SeedGenerator<ID, ResultType> &sg)
    {
        if (!is.good())
            return is;

        result_type s;
        skip_type div;
        skip_type rem;
        is >> std::ws >> s;
        is >> std::ws >> div;
        is >> std::ws >> rem;

        if (is.good()) {
            sg.modulo(div, rem);
            sg.set(s);
        }

        return is;
    }

    private:
    std::atomic<result_type> seed_;
    result_type seed_max_;
    skip_type divisor_;
    skip_type remainder_;

    SeedGenerator() : seed_(0), seed_max_(0), divisor_(1), remainder_(0)
    {
        modulo(divisor_, remainder_);
    }
}; // class SeedGenerator

template <typename ID, typename ResultType, std::size_t K>
class SeedGenerator<ID, std::array<ResultType, K>>
{
    static_assert(std::is_unsigned<ResultType>::value,
        "**SeedGenerator** USED WITH ResultType OTHER THAN UNSIGEND INTEGER "
        "TYPES");

    public:
    using result_type = std::array<ResultType, K>;
    using skip_type = ResultType;

    SeedGenerator(
        const SeedGenerator<ID, std::array<ResultType, K>> &) = delete;

    SeedGenerator<ID, std::array<ResultType, K>> &operator=(
        const SeedGenerator<ID, std::array<ResultType, K>> &) = delete;

    static SeedGenerator<ID, std::array<ResultType, K>> &instance()
    {
        static SeedGenerator<ID, std::array<ResultType, K>> seed;

        return seed;
    }

    template <typename RNGType>
    void seed_rng(RNGType &rng)
    {
        seed_rng_dispatch(rng,
            std::integral_constant<bool,
                              std::is_same<result_type,
                                       internal::KeyType<RNGType>>::value>());
    }

    result_type get()
    {
        std::lock_guard<std::mutex> lock_(mtx_);
        skip();

        return seed_;
    }

    ResultType get_scalar()
    {
        result_type s1(get());
        result_type s2(get());
        for (std::size_t k = 0; k != K; ++k)
            if (s1[k] != s2[k])
                return s2[k];

        return std::get<0>(s2);
    }

    void set(ResultType s)
    {
        seed_.fill(0);
        seed_.front() = s;
    }

    void set(result_type seed) { seed_ = seed; }

    result_type seed() const { return seed_; }

    result_type seed_max() const { return seed_max_; }

    skip_type divisor() const { return divisor_; }

    skip_type remainder() const { return remainder_; }

    void modulo(skip_type div, skip_type rem)
    {
        VSMC_RUNTIME_WARNING_RNG_SEED_GENERATOR_MODULO(div, rem);

        divisor_ = div;
        remainder_ = rem;
        seed_max_.fill(std::numeric_limits<skip_type>::max());

        set(seed_);
    }

    void skip(skip_type steps) { increment(seed_, steps); }

    void skip() { increment(seed_); }

    template <typename CharT, typename Traits>
    friend std::basic_ostream<CharT, Traits> &operator<<(
        std::basic_ostream<CharT, Traits> &os,
        const SeedGenerator<ID, std::array<ResultType, K>> &sg)
    {
        if (!os.good())
            return os;

        os << sg.seed_ << ' ';
        os << sg.divisor_ << ' ';
        os << sg.remainder_ << ' ';

        return os;
    }

    template <typename CharT, typename Traits>
    friend std::basic_istream<CharT, Traits> &operator>>(
        std::basic_istream<CharT, Traits> &is,
        SeedGenerator<ID, std::array<ResultType, K>> &sg)
    {
        if (!is.good())
            return is;

        result_type s;
        skip_type div;
        skip_type rem;
        is >> std::ws >> s;
        is >> std::ws >> div;
        is >> std::ws >> rem;

        if (is.good()) {
            sg.modulo(div, rem);
            sg.set(s);
        }

        return is;
    }

    private:
    result_type seed_;
    result_type seed_max_;
    skip_type divisor_;
    skip_type remainder_;
    std::mutex mtx_;

    SeedGenerator() : divisor_(1), remainder_(0)
    {
        seed_.fill(0);
        seed_max_.fill(0);
        modulo(divisor_, remainder_);
    }

    template <typename RNGType>
    void seed_rng_dispatch(RNGType &rng, std::true_type)
    {
        rng.seed(get());
    }

    template <typename RNGType>
    void seed_rng_dispatch(RNGType &rng, std::false_type)
    {
        rng.seed(get_scalar());
    }
}; // class SeedGenerator

using Seed = SeedGenerator<NullType, VSMC_SEED_RESULT_TYPE>;

} // namespace vsmc

#endif // VSMC_RNG_SEED_HPP