X-Git-Url: https://git.donarmstrong.com/?p=rsem.git;a=blobdiff_plain;f=boost%2Frandom%2Funiform_int_distribution.hpp;fp=boost%2Frandom%2Funiform_int_distribution.hpp;h=0612028ea91422866b944ed93586b4719d77b941;hp=0000000000000000000000000000000000000000;hb=2d71eb92104693ca9baa5a2e1c23eeca776d8fd3;hpb=da57529b92adbb7ae74a89861cb39fb35ac7c62d diff --git a/boost/random/uniform_int_distribution.hpp b/boost/random/uniform_int_distribution.hpp new file mode 100644 index 0000000..0612028 --- /dev/null +++ b/boost/random/uniform_int_distribution.hpp @@ -0,0 +1,400 @@ +/* boost random/uniform_int_distribution.hpp header file + * + * Copyright Jens Maurer 2000-2001 + * Copyright Steven Watanabe 2011 + * Distributed under the Boost Software License, Version 1.0. (See + * accompanying file LICENSE_1_0.txt or copy at + * http://www.boost.org/LICENSE_1_0.txt) + * + * See http://www.boost.org for most recent version including documentation. + * + * $Id: uniform_int_distribution.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $ + * + * Revision history + * 2001-04-08 added min +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +namespace boost { +namespace random { +namespace detail { + + +#ifdef BOOST_MSVC +#pragma warning(push) +// disable division by zero warning, since we can't +// actually divide by zero. +#pragma warning(disable:4723) +#endif + +template +T generate_uniform_int( + Engine& eng, T min_value, T max_value, + boost::mpl::true_ /** is_integral */) +{ + typedef T result_type; + typedef typename make_unsigned::type range_type; + typedef typename Engine::result_type base_result; + // ranges are always unsigned + typedef typename make_unsigned::type base_unsigned; + const range_type range = random::detail::subtract()(max_value, min_value); + const base_result bmin = (eng.min)(); + const base_unsigned brange = + random::detail::subtract()((eng.max)(), (eng.min)()); + + if(range == 0) { + return min_value; + } else if(brange == range) { + // this will probably never happen in real life + // basically nothing to do; just take care we don't overflow / underflow + base_unsigned v = random::detail::subtract()(eng(), bmin); + return random::detail::add()(v, min_value); + } else if(brange < range) { + // use rejection method to handle things like 0..3 --> 0..4 + for(;;) { + // concatenate several invocations of the base RNG + // take extra care to avoid overflows + + // limit == floor((range+1)/(brange+1)) + // Therefore limit*(brange+1) <= range+1 + range_type limit; + if(range == (std::numeric_limits::max)()) { + limit = range/(range_type(brange)+1); + if(range % (range_type(brange)+1) == range_type(brange)) + ++limit; + } else { + limit = (range+1)/(range_type(brange)+1); + } + + // We consider "result" as expressed to base (brange+1): + // For every power of (brange+1), we determine a random factor + range_type result = range_type(0); + range_type mult = range_type(1); + + // loop invariants: + // result < mult + // mult <= range + while(mult <= limit) { + // Postcondition: result <= range, thus no overflow + // + // limit*(brange+1)<=range+1 def. of limit (1) + // eng()-bmin<=brange eng() post. (2) + // and mult<=limit. loop condition (3) + // Therefore mult*(eng()-bmin+1)<=range+1 by (1),(2),(3) (4) + // Therefore mult*(eng()-bmin)+mult<=range+1 rearranging (4) (5) + // result(random::detail::subtract()(eng(), bmin) * mult); + + // equivalent to (mult * (brange+1)) == range+1, but avoids overflow. + if(mult * range_type(brange) == range - mult + 1) { + // The destination range is an integer power of + // the generator's range. + return(result); + } + + // Postcondition: mult <= range + // + // limit*(brange+1)<=range+1 def. of limit (1) + // mult<=limit loop condition (2) + // Therefore mult*(brange+1)<=range+1 by (1), (2) (3) + // mult*(brange+1)!=range+1 preceding if (4) + // Therefore mult*(brange+1) limit loop condition (1) + // Suppose range/mult >= brange+1 Assumption (2) + // range >= mult*(brange+1) by (2) (3) + // range+1 > mult*(brange+1) by (3) (4) + // range+1 > (limit+1)*(brange+1) by (1), (4) (5) + // (range+1)/(brange+1) > limit+1 by (5) (6) + // limit < floor((range+1)/(brange+1)) by (6) (7) + // limit==floor((range+1)/(brange+1)) def. of limit (8) + // not (2) reductio (9) + // + // loop postcondition: (range/mult)*mult+(mult-1) >= range + // + // (range/mult)*mult + range%mult == range identity (1) + // range%mult < mult def. of % (2) + // (range/mult)*mult+mult > range by (1), (2) (3) + // (range/mult)*mult+(mult-1) >= range by (3) (4) + // + // Note that the maximum value of result at this point is (mult-1), + // so after this final step, we generate numbers that can be + // at least as large as range. We have to really careful to avoid + // overflow in this final addition and in the rejection. Anything + // that overflows is larger than range and can thus be rejected. + + // range/mult < brange+1 -> no endless loop + range_type result_increment = + generate_uniform_int( + eng, + static_cast(0), + static_cast(range/mult), + boost::mpl::true_()); + if((std::numeric_limits::max)() / mult < result_increment) { + // The multiplcation would overflow. Reject immediately. + continue; + } + result_increment *= mult; + // unsigned integers are guaranteed to wrap on overflow. + result += result_increment; + if(result < result_increment) { + // The addition overflowed. Reject. + continue; + } + if(result > range) { + // Too big. Reject. + continue; + } + return random::detail::add()(result, min_value); + } + } else { // brange > range + base_unsigned bucket_size; + // it's safe to add 1 to range, as long as we cast it first, + // because we know that it is less than brange. However, + // we do need to be careful not to cause overflow by adding 1 + // to brange. + if(brange == (std::numeric_limits::max)()) { + bucket_size = brange / (static_cast(range)+1); + if(brange % (static_cast(range)+1) == static_cast(range)) { + ++bucket_size; + } + } else { + bucket_size = (brange+1) / (static_cast(range)+1); + } + for(;;) { + base_unsigned result = + random::detail::subtract()(eng(), bmin); + result /= bucket_size; + // result and range are non-negative, and result is possibly larger + // than range, so the cast is safe + if(result <= static_cast(range)) + return random::detail::add()(result, min_value); + } + } +} + +#ifdef BOOST_MSVC +#pragma warning(pop) +#endif + +template +inline T generate_uniform_int( + Engine& eng, T min_value, T max_value, + boost::mpl::false_ /** is_integral */) +{ + uniform_int_float wrapper(eng); + return generate_uniform_int(wrapper, min_value, max_value, boost::mpl::true_()); +} + +template +inline T generate_uniform_int(Engine& eng, T min_value, T max_value) +{ + typedef typename Engine::result_type base_result; + return generate_uniform_int(eng, min_value, max_value, + boost::is_integral()); +} + +} + +/** + * The class template uniform_int_distribution models a \random_distribution. + * On each invocation, it returns a random integer value uniformly + * distributed in the set of integers {min, min+1, min+2, ..., max}. + * + * The template parameter IntType shall denote an integer-like value type. + */ +template +class uniform_int_distribution +{ +public: + typedef IntType input_type; + typedef IntType result_type; + + class param_type + { + public: + + typedef uniform_int_distribution distribution_type; + + /** + * Constructs the parameters of a uniform_int_distribution. + * + * Requires min <= max + */ + explicit param_type( + IntType min_arg = 0, + IntType max_arg = (std::numeric_limits::max)()) + : _min(min_arg), _max(max_arg) + { + BOOST_ASSERT(_min <= _max); + } + + /** Returns the minimum value of the distribution. */ + IntType a() const { return _min; } + /** Returns the maximum value of the distribution. */ + IntType b() const { return _max; } + + /** Writes the parameters to a @c std::ostream. */ + BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm) + { + os << parm._min << " " << parm._max; + return os; + } + + /** Reads the parameters from a @c std::istream. */ + BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm) + { + IntType min_in, max_in; + if(is >> min_in >> std::ws >> max_in) { + if(min_in <= max_in) { + parm._min = min_in; + parm._max = max_in; + } else { + is.setstate(std::ios_base::failbit); + } + } + return is; + } + + /** Returns true if the two sets of parameters are equal. */ + BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs) + { return lhs._min == rhs._min && lhs._max == rhs._max; } + + /** Returns true if the two sets of parameters are different. */ + BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type) + + private: + + IntType _min; + IntType _max; + }; + + /** + * Constructs a uniform_int_distribution. @c min and @c max are + * the parameters of the distribution. + * + * Requires: min <= max + */ + explicit uniform_int_distribution( + IntType min_arg = 0, + IntType max_arg = (std::numeric_limits::max)()) + : _min(min_arg), _max(max_arg) + { + BOOST_ASSERT(min_arg <= max_arg); + } + /** Constructs a uniform_int_distribution from its parameters. */ + explicit uniform_int_distribution(const param_type& parm) + : _min(parm.a()), _max(parm.b()) {} + + /** Returns the minimum value of the distribution */ + IntType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; } + /** Returns the maximum value of the distribution */ + IntType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; } + + /** Returns the minimum value of the distribution */ + IntType a() const { return _min; } + /** Returns the maximum value of the distribution */ + IntType b() const { return _max; } + + /** Returns the parameters of the distribution. */ + param_type param() const { return param_type(_min, _max); } + /** Sets the parameters of the distribution. */ + void param(const param_type& parm) + { + _min = parm.a(); + _max = parm.b(); + } + + /** + * Effects: Subsequent uses of the distribution do not depend + * on values produced by any engine prior to invoking reset. + */ + void reset() { } + + /** Returns an integer uniformly distributed in the range [min, max]. */ + template + result_type operator()(Engine& eng) const + { return detail::generate_uniform_int(eng, _min, _max); } + + /** + * Returns an integer uniformly distributed in the range + * [param.a(), param.b()]. + */ + template + result_type operator()(Engine& eng, const param_type& parm) const + { return detail::generate_uniform_int(eng, parm.a(), parm.b()); } + + /** Writes the distribution to a @c std::ostream. */ + BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, uniform_int_distribution, ud) + { + os << ud.param(); + return os; + } + + /** Reads the distribution from a @c std::istream. */ + BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, uniform_int_distribution, ud) + { + param_type parm; + if(is >> parm) { + ud.param(parm); + } + return is; + } + + /** + * Returns true if the two distributions will produce identical sequences + * of values given equal generators. + */ + BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(uniform_int_distribution, lhs, rhs) + { return lhs._min == rhs._min && lhs._max == rhs._max; } + + /** + * Returns true if the two distributions may produce different sequences + * of values given equal generators. + */ + BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(uniform_int_distribution) + +private: + IntType _min; + IntType _max; +}; + +} // namespace random +} // namespace boost + +#endif // BOOST_RANDOM_UNIFORM_INT_HPP