comparison DEPENDENCIES/generic/include/boost/random/independent_bits.hpp @ 16:2665513ce2d3

Add boost headers

+/* boost random/independent_bits.hpp header file
+ *
+ * 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: independent_bits.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $
+ *
+ */
+
+#ifndef BOOST_RANDOM_INDEPENDENT_BITS_HPP
+#define BOOST_RANDOM_INDEPENDENT_BITS_HPP
+
+#include <istream>
+#include <iosfwd>
+#include <boost/assert.hpp>
+#include <boost/limits.hpp>
+#include <boost/config.hpp>
+#include <boost/cstdint.hpp>
+#include <boost/integer/integer_mask.hpp>
+#include <boost/type_traits/make_unsigned.hpp>
+#include <boost/random/detail/config.hpp>
+#include <boost/random/detail/integer_log2.hpp>
+#include <boost/random/detail/operators.hpp>
+#include <boost/random/detail/seed.hpp>
+#include <boost/random/detail/seed_impl.hpp>
+#include <boost/random/detail/signed_unsigned_tools.hpp>
+
+namespace boost {
+namespace random {
+
+/**
+ * An instantiation of class template @c independent_bits_engine
+ * model a \pseudo_random_number_generator.  It generates random
+ * numbers distributed between [0, 2^w) by combining one or
+ * more invocations of the base engine.
+ *
+ * Requires: 0 < w <= std::numeric_limits<UIntType>::digits
+ */
+template<class Engine, std::size_t w, class UIntType>
+class independent_bits_engine
+{
+public:
+    typedef Engine base_type;
+    typedef UIntType result_type;
+
+    // Required by old Boost.Random concept
+    BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
+
+    /** Returns the smallest value that the generator can produce. */
+    static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION ()
+    { return 0; }
+    /** Returns the largest value that the generator can produce. */
+    static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION ()
+    { return boost::low_bits_mask_t<w>::sig_bits; }
+
+    /**
+     * Constructs an @c independent_bits_engine using the
+     * default constructor of the base generator.
+     */
+    independent_bits_engine() { }
+
+    /**
+     * Constructs an @c independent_bits_engine, using seed as
+     * the constructor argument for both base generators.
+     */
+    BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(independent_bits_engine,
+        result_type, seed_arg)
+    {
+        _base.seed(seed_arg);
+    }
+
+    /**
+     * Constructs an @c independent_bits_engine, using seq as
+     * the constructor argument for the base generator.
+     */
+    BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(independent_bits_engine,
+        SeedSeq, seq)
+    { _base.seed(seq); }
+
+    /** Constructs an @c independent_bits_engine by copying @c base. */
+    independent_bits_engine(const base_type& base_arg) : _base(base_arg) {}
+
+    /**
+     * Contructs an @c independent_bits_engine with
+     * values from the range defined by the input iterators first
+     * and last.  first will be modified to point to the element
+     * after the last one used.
+     *
+     * Throws: @c std::invalid_argument if the input range is too small.
+     *
+     * Exception Safety: Basic
+     */
+    template<class It>
+    independent_bits_engine(It& first, It last) : _base(first, last) { }
+
+    /**
+     * Seeds an @c independent_bits_engine using the default
+     * seed of the base generator.
+     */
+    void seed() { _base.seed(); }
+
+    /**
+     * Seeds an @c independent_bits_engine, using @c seed as the
+     * seed for the base generator.
+     */
+    BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(independent_bits_engine,
+        result_type, seed_arg)
+    { _base.seed(seed_arg); }
+
+    /**
+     * Seeds an @c independent_bits_engine, using @c seq to
+     * seed the base generator.
+     */
+    BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(independent_bits_engine,
+        SeedSeq, seq)
+    { _base.seed(seq); }
+
+    /**
+     * Seeds an @c independent_bits_engine with
+     * values from the range defined by the input iterators first
+     * and last.  first will be modified to point to the element
+     * after the last one used.
+     *
+     * Throws: @c std::invalid_argument if the input range is too small.
+     *
+     * Exception Safety: Basic
+     */
+    template<class It> void seed(It& first, It last)
+    { _base.seed(first, last); }
+
+    /** Returns the next value of the generator. */
+    result_type operator()()
+    {
+        // While it may seem wasteful to recalculate this
+        // every time, both msvc and gcc can propagate
+        // constants, resolving this at compile time.
+        base_unsigned range =
+            detail::subtract<base_result>()((_base.max)(), (_base.min)());
+        std::size_t m =
+            (range == (std::numeric_limits<base_unsigned>::max)()) ?
+                std::numeric_limits<base_unsigned>::digits :
+                detail::integer_log2(range + 1);
+        std::size_t n = (w + m - 1) / m;
+        std::size_t w0, n0;
+        base_unsigned y0, y1;
+        base_unsigned y0_mask, y1_mask;
+        calc_params(n, range, w0, n0, y0, y1, y0_mask, y1_mask);
+        if(base_unsigned(range - y0 + 1) > y0 / n) {
+            // increment n and try again.
+            ++n;
+            calc_params(n, range, w0, n0, y0, y1, y0_mask, y1_mask);
+        }
+
+        BOOST_ASSERT(n0*w0 + (n - n0)*(w0 + 1) == w);
+
+        result_type S = 0;
+        for(std::size_t k = 0; k < n0; ++k) {
+            base_unsigned u;
+            do {
+                u = detail::subtract<base_result>()(_base(), (_base.min)());
+            } while(u > base_unsigned(y0 - 1));
+            S = (S << w0) + (u & y0_mask);
+        }
+        for(std::size_t k = 0; k < (n - n0); ++k) {
+            base_unsigned u;
+            do {
+                u = detail::subtract<base_result>()(_base(), (_base.min)());
+            } while(u > base_unsigned(y1 - 1));
+            S = (S << (w0 + 1)) + (u & y1_mask);
+        }
+        return S;
+    }
+  
+    /** Fills a range with random values */
+    template<class Iter>
+    void generate(Iter first, Iter last)
+    { detail::generate_from_int(*this, first, last); }
+
+    /** Advances the state of the generator by @c z. */
+    void discard(boost::uintmax_t z)
+    {
+        for(boost::uintmax_t i = 0; i < z; ++i) {
+            (*this)();
+        }
+    }
+
+    const base_type& base() const { return _base; }
+
+    /**
+     * Writes the textual representation if the generator to a @c std::ostream.
+     * The textual representation of the engine is the textual representation
+     * of the base engine.
+     */
+    BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, independent_bits_engine, r)
+    {
+        os << r._base;
+        return os;
+    }
+
+    /**
+     * Reads the state of an @c independent_bits_engine from a
+     * @c std::istream.
+     */
+    BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, independent_bits_engine, r)
+    {
+        is >> r._base;
+        return is;
+    }
+
+    /**
+     * Returns: true iff the two @c independent_bits_engines will
+     * produce the same sequence of values.
+     */
+    BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(independent_bits_engine, x, y)
+    { return x._base == y._base; }
+    /**
+     * Returns: true iff the two @c independent_bits_engines will
+     * produce different sequences of values.
+     */
+    BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(independent_bits_engine)
+
+private:
+
+    /// \cond show_private
+    typedef typename base_type::result_type base_result;
+    typedef typename make_unsigned<base_result>::type base_unsigned;
+
+    void calc_params(
+        std::size_t n, base_unsigned range,
+        std::size_t& w0, std::size_t& n0,
+        base_unsigned& y0, base_unsigned& y1,
+        base_unsigned& y0_mask, base_unsigned& y1_mask)
+    {
+        BOOST_ASSERT(w >= n);
+        w0 = w/n;
+        n0 = n - w % n;
+        y0_mask = (base_unsigned(2) << (w0 - 1)) - 1;
+        y1_mask = (y0_mask << 1) | 1;
+        y0 = (range + 1) & ~y0_mask;
+        y1 = (range + 1) & ~y1_mask;
+        BOOST_ASSERT(y0 != 0 || base_unsigned(range + 1) == 0);
+    }
+    /// \endcond
+
+    Engine _base;
+};
+
+#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
+template<class Engine, std::size_t w, class UIntType>
+const bool independent_bits_engine<Engine, w, UIntType>::has_fixed_range;
+#endif
+
+} // namespace random
+} // namespace boost
+
+#endif // BOOST_RANDOM_INDEPENDENT_BITS_HPP