Chris@16: /* boost random/detail/seed.hpp header file
Chris@16:  *
Chris@16:  * Copyright Steven Watanabe 2009
Chris@16:  * Distributed under the Boost Software License, Version 1.0. (See
Chris@16:  * accompanying file LICENSE_1_0.txt or copy at
Chris@16:  * http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  *
Chris@16:  * See http://www.boost.org for most recent version including documentation.
Chris@16:  *
Chris@101:  * $Id$
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_DETAIL_SEED_IMPL_HPP
Chris@16: #define BOOST_RANDOM_DETAIL_SEED_IMPL_HPP
Chris@16: 
Chris@16: #include <stdexcept>
Chris@16: #include <boost/cstdint.hpp>
Chris@101: #include <boost/throw_exception.hpp>
Chris@16: #include <boost/config/no_tr1/cmath.hpp>
Chris@16: #include <boost/integer/integer_mask.hpp>
Chris@16: #include <boost/integer/static_log2.hpp>
Chris@16: #include <boost/type_traits/is_signed.hpp>
Chris@16: #include <boost/type_traits/is_integral.hpp>
Chris@16: #include <boost/type_traits/make_unsigned.hpp>
Chris@16: #include <boost/mpl/bool.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/mpl/int.hpp>
Chris@16: #include <boost/random/detail/const_mod.hpp>
Chris@16: #include <boost/random/detail/integer_log2.hpp>
Chris@16: #include <boost/random/detail/signed_unsigned_tools.hpp>
Chris@16: #include <boost/random/detail/generator_bits.hpp>
Chris@16: 
Chris@16: #include <boost/random/detail/disable_warnings.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: namespace detail {
Chris@16: 
Chris@16: // finds the seed type of an engine, given its
Chris@16: // result_type.  If the result_type is integral
Chris@16: // the seed type is the same.  If the result_type
Chris@16: // is floating point, the seed type is uint32_t
Chris@16: template<class T>
Chris@16: struct seed_type
Chris@16: {
Chris@16:     typedef typename boost::mpl::if_<boost::is_integral<T>,
Chris@16:         T,
Chris@16:         boost::uint32_t
Chris@16:     >::type type;
Chris@16: };
Chris@16: 
Chris@16: template<int N>
Chris@16: struct const_pow_impl
Chris@16: {
Chris@16:     template<class T>
Chris@16:     static T call(T arg, int n, T result)
Chris@16:     {
Chris@16:         return const_pow_impl<N / 2>::call(arg * arg, n / 2,
Chris@16:             n%2 == 0? result : result * arg);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: template<>
Chris@16: struct const_pow_impl<0>
Chris@16: {
Chris@16:     template<class T>
Chris@16:     static T call(T, int, T result)
Chris@16:     {
Chris@16:         return result;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: // requires N is an upper bound on n
Chris@16: template<int N, class T>
Chris@16: inline T const_pow(T arg, int n) { return const_pow_impl<N>::call(arg, n, T(1)); }
Chris@16: 
Chris@16: template<class T>
Chris@16: inline T pow2(int n)
Chris@16: {
Chris@16:     typedef unsigned int_type;
Chris@16:     const int max_bits = std::numeric_limits<int_type>::digits;
Chris@16:     T multiplier = T(int_type(1) << (max_bits - 1)) * 2;
Chris@16:     return (int_type(1) << (n % max_bits)) *
Chris@16:         const_pow<std::numeric_limits<T>::digits / max_bits>(multiplier, n / max_bits);
Chris@16: }
Chris@16: 
Chris@16: template<class Engine, class Iter>
Chris@16: void generate_from_real(Engine& eng, Iter begin, Iter end)
Chris@16: {
Chris@16:     using std::fmod;
Chris@16:     typedef typename Engine::result_type RealType;
Chris@16:     const int Bits = detail::generator_bits<Engine>::value();
Chris@16:     int remaining_bits = 0;
Chris@16:     boost::uint_least32_t saved_bits = 0;
Chris@16:     RealType multiplier = pow2<RealType>( Bits);
Chris@16:     RealType mult32 = RealType(4294967296.0); // 2^32
Chris@16:     while(true) {
Chris@16:         RealType val = eng() * multiplier;
Chris@16:         int available_bits = Bits;
Chris@16:         // Make sure the compiler can optimize this out
Chris@16:         // if it isn't possible.
Chris@16:         if(Bits < 32 && available_bits < 32 - remaining_bits) {
Chris@16:             saved_bits |= boost::uint_least32_t(val) << remaining_bits;
Chris@16:             remaining_bits += Bits;
Chris@16:         } else {
Chris@16:             // If Bits < 32, then remaining_bits != 0, since
Chris@16:             // if remaining_bits == 0, available_bits < 32 - 0,
Chris@16:             // and we won't get here to begin with.
Chris@16:             if(Bits < 32 || remaining_bits != 0) {
Chris@16:                 boost::uint_least32_t divisor =
Chris@16:                     (boost::uint_least32_t(1) << (32 - remaining_bits));
Chris@16:                 boost::uint_least32_t extra_bits = boost::uint_least32_t(fmod(val, mult32)) & (divisor - 1);
Chris@16:                 val = val / divisor;
Chris@16:                 *begin++ = saved_bits | (extra_bits << remaining_bits);
Chris@16:                 if(begin == end) return;
Chris@16:                 available_bits -= 32 - remaining_bits;
Chris@16:                 remaining_bits = 0;
Chris@16:             }
Chris@16:             // If Bits < 32 we should never enter this loop
Chris@16:             if(Bits >= 32) {
Chris@16:                 for(; available_bits >= 32; available_bits -= 32) {
Chris@16:                     boost::uint_least32_t word = boost::uint_least32_t(fmod(val, mult32));
Chris@16:                     val /= mult32;
Chris@16:                     *begin++ = word;
Chris@16:                     if(begin == end) return;
Chris@16:                 }
Chris@16:             }
Chris@16:             remaining_bits = available_bits;
Chris@16:             saved_bits = static_cast<boost::uint_least32_t>(val);
Chris@16:         }
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: template<class Engine, class Iter>
Chris@16: void generate_from_int(Engine& eng, Iter begin, Iter end)
Chris@16: {
Chris@16:     typedef typename Engine::result_type IntType;
Chris@16:     typedef typename boost::make_unsigned<IntType>::type unsigned_type;
Chris@16:     int remaining_bits = 0;
Chris@16:     boost::uint_least32_t saved_bits = 0;
Chris@16:     unsigned_type range = boost::random::detail::subtract<IntType>()((eng.max)(), (eng.min)());
Chris@16: 
Chris@16:     int bits =
Chris@16:         (range == (std::numeric_limits<unsigned_type>::max)()) ?
Chris@16:             std::numeric_limits<unsigned_type>::digits :
Chris@16:             detail::integer_log2(range + 1);
Chris@16: 
Chris@16:     {
Chris@16:         int discarded_bits = detail::integer_log2(bits);
Chris@16:         unsigned_type excess = (range + 1) >> (bits - discarded_bits);
Chris@16:         if(excess != 0) {
Chris@16:             int extra_bits = detail::integer_log2((excess - 1) ^ excess);
Chris@16:             bits = bits - discarded_bits + extra_bits;
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     unsigned_type mask = (static_cast<unsigned_type>(2) << (bits - 1)) - 1;
Chris@16:     unsigned_type limit = ((range + 1) & ~mask) - 1;
Chris@16: 
Chris@16:     while(true) {
Chris@16:         unsigned_type val;
Chris@16:         do {
Chris@16:             val = boost::random::detail::subtract<IntType>()(eng(), (eng.min)());
Chris@16:         } while(limit != range && val > limit);
Chris@16:         val &= mask;
Chris@16:         int available_bits = bits;
Chris@16:         if(available_bits == 32) {
Chris@16:             *begin++ = static_cast<boost::uint_least32_t>(val) & 0xFFFFFFFFu;
Chris@16:             if(begin == end) return;
Chris@16:         } else if(available_bits % 32 == 0) {
Chris@16:             for(int i = 0; i < available_bits / 32; ++i) {
Chris@16:                 boost::uint_least32_t word = boost::uint_least32_t(val) & 0xFFFFFFFFu;
Chris@101:                 int suppress_warning = (bits >= 32);
Chris@101:                 BOOST_ASSERT(suppress_warning == 1);
Chris@101:                 val >>= (32 * suppress_warning);
Chris@16:                 *begin++ = word;
Chris@16:                 if(begin == end) return;
Chris@16:             }
Chris@16:         } else if(bits < 32 && available_bits < 32 - remaining_bits) {
Chris@16:             saved_bits |= boost::uint_least32_t(val) << remaining_bits;
Chris@16:             remaining_bits += bits;
Chris@16:         } else {
Chris@16:             if(bits < 32 || remaining_bits != 0) {
Chris@16:                 boost::uint_least32_t extra_bits = boost::uint_least32_t(val) & ((boost::uint_least32_t(1) << (32 - remaining_bits)) - 1);
Chris@16:                 val >>= 32 - remaining_bits;
Chris@16:                 *begin++ = saved_bits | (extra_bits << remaining_bits);
Chris@16:                 if(begin == end) return;
Chris@16:                 available_bits -= 32 - remaining_bits;
Chris@16:                 remaining_bits = 0;
Chris@16:             }
Chris@16:             if(bits >= 32) {
Chris@16:                 for(; available_bits >= 32; available_bits -= 32) {
Chris@16:                     boost::uint_least32_t word = boost::uint_least32_t(val) & 0xFFFFFFFFu;
Chris@101:                     int suppress_warning = (bits >= 32);
Chris@101:                     BOOST_ASSERT(suppress_warning == 1);
Chris@101:                     val >>= (32 * suppress_warning);
Chris@16:                     *begin++ = word;
Chris@16:                     if(begin == end) return;
Chris@16:                 }
Chris@16:             }
Chris@16:             remaining_bits = available_bits;
Chris@16:             saved_bits = static_cast<boost::uint_least32_t>(val);
Chris@16:         }
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: template<class Engine, class Iter>
Chris@16: void generate_impl(Engine& eng, Iter first, Iter last, boost::mpl::true_)
Chris@16: {
Chris@16:     return detail::generate_from_int(eng, first, last);
Chris@16: }
Chris@16: 
Chris@16: template<class Engine, class Iter>
Chris@16: void generate_impl(Engine& eng, Iter first, Iter last, boost::mpl::false_)
Chris@16: {
Chris@16:     return detail::generate_from_real(eng, first, last);
Chris@16: }
Chris@16: 
Chris@16: template<class Engine, class Iter>
Chris@16: void generate(Engine& eng, Iter first, Iter last)
Chris@16: {
Chris@16:     return detail::generate_impl(eng, first, last, boost::is_integral<typename Engine::result_type>());
Chris@16: }
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: template<class IntType, IntType m, class SeedSeq>
Chris@16: IntType seed_one_int(SeedSeq& seq)
Chris@16: {
Chris@16:     static const int log = ::boost::mpl::if_c<(m == 0),
Chris@16:         ::boost::mpl::int_<(::std::numeric_limits<IntType>::digits)>,
Chris@16:         ::boost::static_log2<m> >::type::value;
Chris@16:     static const int k =
Chris@16:         (log + ((~(static_cast<IntType>(2) << (log - 1)) & m)? 32 : 31)) / 32;
Chris@16:     ::boost::uint_least32_t array[log / 32 + 4];
Chris@16:     seq.generate(&array[0], &array[0] + k + 3);
Chris@16:     IntType s = 0;
Chris@16:     for(int j = 0; j < k; ++j) {
Chris@16:         IntType digit = const_mod<IntType, m>::apply(IntType(array[j+3]));
Chris@16:         IntType mult = IntType(1) << 32*j;
Chris@16:         s = const_mod<IntType, m>::mult_add(mult, digit, s);
Chris@16:     }
Chris@16:     return s;
Chris@16: }
Chris@16: 
Chris@16: template<class IntType, IntType m, class Iter>
Chris@16: IntType get_one_int(Iter& first, Iter last)
Chris@16: {
Chris@16:     static const int log = ::boost::mpl::if_c<(m == 0),
Chris@16:         ::boost::mpl::int_<(::std::numeric_limits<IntType>::digits)>,
Chris@16:         ::boost::static_log2<m> >::type::value;
Chris@16:     static const int k =
Chris@16:         (log + ((~(static_cast<IntType>(2) << (log - 1)) & m)? 32 : 31)) / 32;
Chris@16:     IntType s = 0;
Chris@16:     for(int j = 0; j < k; ++j) {
Chris@16:         if(first == last) {
Chris@101:             boost::throw_exception(::std::invalid_argument("Not enough elements in call to seed."));
Chris@16:         }
Chris@16:         IntType digit = const_mod<IntType, m>::apply(IntType(*first++));
Chris@16:         IntType mult = IntType(1) << 32*j;
Chris@16:         s = const_mod<IntType, m>::mult_add(mult, digit, s);
Chris@16:     }
Chris@16:     return s;
Chris@16: }
Chris@16: 
Chris@16: // TODO: work in-place whenever possible
Chris@16: template<int w, std::size_t n, class SeedSeq, class UIntType>
Chris@16: void seed_array_int_impl(SeedSeq& seq, UIntType (&x)[n])
Chris@16: {
Chris@16:     boost::uint_least32_t storage[((w+31)/32) * n];
Chris@16:     seq.generate(&storage[0], &storage[0] + ((w+31)/32) * n);
Chris@16:     for(std::size_t j = 0; j < n; j++) {
Chris@16:         UIntType val = 0;
Chris@16:         for(std::size_t k = 0; k < (w+31)/32; ++k) {
Chris@16:             val += static_cast<UIntType>(storage[(w+31)/32*j + k]) << 32*k;
Chris@16:         }
Chris@16:         x[j] = val & ::boost::low_bits_mask_t<w>::sig_bits;
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class SeedSeq, class IntType>
Chris@16: inline void seed_array_int_impl(SeedSeq& seq, IntType (&x)[n], boost::mpl::true_)
Chris@16: {
Chris@16:     typedef typename boost::make_unsigned<IntType>::type unsigned_array[n];
Chris@16:     seed_array_int_impl<w>(seq, reinterpret_cast<unsigned_array&>(x));
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class SeedSeq, class IntType>
Chris@16: inline void seed_array_int_impl(SeedSeq& seq, IntType (&x)[n], boost::mpl::false_)
Chris@16: {
Chris@16:     seed_array_int_impl<w>(seq, x);
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class SeedSeq, class IntType>
Chris@16: inline void seed_array_int(SeedSeq& seq, IntType (&x)[n])
Chris@16: {
Chris@16:     seed_array_int_impl<w>(seq, x, boost::is_signed<IntType>());
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class Iter, class UIntType>
Chris@16: void fill_array_int_impl(Iter& first, Iter last, UIntType (&x)[n])
Chris@16: {
Chris@16:     for(std::size_t j = 0; j < n; j++) {
Chris@16:         UIntType val = 0;
Chris@16:         for(std::size_t k = 0; k < (w+31)/32; ++k) {
Chris@16:             if(first == last) {
Chris@101:                 boost::throw_exception(std::invalid_argument("Not enough elements in call to seed."));
Chris@16:             }
Chris@16:             val += static_cast<UIntType>(*first++) << 32*k;
Chris@16:         }
Chris@16:         x[j] = val & ::boost::low_bits_mask_t<w>::sig_bits;
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class Iter, class IntType>
Chris@16: inline void fill_array_int_impl(Iter& first, Iter last, IntType (&x)[n], boost::mpl::true_)
Chris@16: {
Chris@16:     typedef typename boost::make_unsigned<IntType>::type unsigned_array[n];
Chris@16:     fill_array_int_impl<w>(first, last, reinterpret_cast<unsigned_array&>(x));
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class Iter, class IntType>
Chris@16: inline void fill_array_int_impl(Iter& first, Iter last, IntType (&x)[n], boost::mpl::false_)
Chris@16: {
Chris@16:     fill_array_int_impl<w>(first, last, x);
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class Iter, class IntType>
Chris@16: inline void fill_array_int(Iter& first, Iter last, IntType (&x)[n])
Chris@16: {
Chris@16:     fill_array_int_impl<w>(first, last, x, boost::is_signed<IntType>());
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class RealType>
Chris@16: void seed_array_real_impl(const boost::uint_least32_t* storage, RealType (&x)[n])
Chris@16: {
Chris@16:     boost::uint_least32_t mask = ~((~boost::uint_least32_t(0)) << (w%32));
Chris@16:     RealType two32 = 4294967296.0;
Chris@16:     const RealType divisor = RealType(1)/detail::pow2<RealType>(w);
Chris@16:     unsigned int j;
Chris@16:     for(j = 0; j < n; ++j) {
Chris@16:         RealType val = RealType(0);
Chris@16:         RealType mult = divisor;
Chris@16:         for(int k = 0; k < w/32; ++k) {
Chris@16:             val += *storage++ * mult;
Chris@16:             mult *= two32;
Chris@16:         }
Chris@16:         if(mask != 0) {
Chris@16:             val += (*storage++ & mask) * mult;
Chris@16:         }
Chris@16:         BOOST_ASSERT(val >= 0);
Chris@16:         BOOST_ASSERT(val < 1);
Chris@16:         x[j] = val;
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class SeedSeq, class RealType>
Chris@16: void seed_array_real(SeedSeq& seq, RealType (&x)[n])
Chris@16: {
Chris@16:     using std::pow;
Chris@16:     boost::uint_least32_t storage[((w+31)/32) * n];
Chris@16:     seq.generate(&storage[0], &storage[0] + ((w+31)/32) * n);
Chris@16:     seed_array_real_impl<w>(storage, x);
Chris@16: }
Chris@16: 
Chris@16: template<int w, std::size_t n, class Iter, class RealType>
Chris@16: void fill_array_real(Iter& first, Iter last, RealType (&x)[n])
Chris@16: {
Chris@16:     boost::uint_least32_t mask = ~((~boost::uint_least32_t(0)) << (w%32));
Chris@16:     RealType two32 = 4294967296.0;
Chris@16:     const RealType divisor = RealType(1)/detail::pow2<RealType>(w);
Chris@16:     unsigned int j;
Chris@16:     for(j = 0; j < n; ++j) {
Chris@16:         RealType val = RealType(0);
Chris@16:         RealType mult = divisor;
Chris@16:         for(int k = 0; k < w/32; ++k, ++first) {
Chris@101:             if(first == last) boost::throw_exception(std::invalid_argument("Not enough elements in call to seed."));
Chris@16:             val += *first * mult;
Chris@16:             mult *= two32;
Chris@16:         }
Chris@16:         if(mask != 0) {
Chris@101:             if(first == last) boost::throw_exception(std::invalid_argument("Not enough elements in call to seed."));
Chris@16:             val += (*first & mask) * mult;
Chris@16:             ++first;
Chris@16:         }
Chris@16:         BOOST_ASSERT(val >= 0);
Chris@16:         BOOST_ASSERT(val < 1);
Chris@16:         x[j] = val;
Chris@16:     }
Chris@16: }
Chris@16: 
Chris@16: }
Chris@16: }
Chris@16: }
Chris@16: 
Chris@16: #include <boost/random/detail/enable_warnings.hpp>
Chris@16: 
Chris@16: #endif