Imported Upstream version 1.49.0upstream/1.49.0

1 files changed, 97 insertions, 0 deletions

diff --git a/boost/random/generate_canonical.hpp b/boost/random/generate_canonical.hpp
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+/* boost random/generate_canonical.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: generate_canonical.hpp 72951 2011-07-07 04:57:37Z steven_watanabe $
+ *
+ */
+
+#ifndef BOOST_RANDOM_GENERATE_CANONICAL_HPP
+#define BOOST_RANDOM_GENERATE_CANONICAL_HPP
+
+#include <algorithm>
+#include <boost/assert.hpp>
+#include <boost/config/no_tr1/cmath.hpp>
+#include <boost/limits.hpp>
+#include <boost/type_traits/is_integral.hpp>
+#include <boost/math/special_functions.hpp>
+#include <boost/random/detail/signed_unsigned_tools.hpp>
+#include <boost/random/detail/generator_bits.hpp>
+
+namespace boost {
+namespace random {
+
+namespace detail {
+
+template<class RealType, std::size_t bits, class URNG>
+RealType generate_canonical_impl(URNG& g, boost::mpl::true_ /*is_integral*/)
+{
+    using std::pow;
+    typedef typename URNG::result_type base_result;
+    std::size_t digits = std::numeric_limits<RealType>::digits;
+    RealType R = RealType((g.max)()) - RealType((g.min)()) + 1;
+    RealType mult = R;
+    RealType limit =
+        pow(RealType(2),
+            RealType((std::min)(static_cast<std::size_t>(bits), digits)));
+    RealType S = RealType(detail::subtract<base_result>()(g(), (g.min)()));
+    while(mult < limit) {
+        RealType inc = RealType(detail::subtract<base_result>()(g(), (g.min)()));
+        S += inc * mult;
+        mult *= R;
+    }
+    return S / mult;
+}
+
+template<class RealType, std::size_t bits, class URNG>
+RealType generate_canonical_impl(URNG& g, boost::mpl::false_ /*is_integral*/)
+{
+    using std::pow;
+    using std::floor;
+    BOOST_ASSERT((g.min)() == 0);
+    BOOST_ASSERT((g.max)() == 1);
+    typedef typename URNG::result_type base_result;
+    std::size_t digits = std::numeric_limits<RealType>::digits;
+    std::size_t engine_bits = detail::generator_bits<URNG>::value();
+    std::size_t b = (std::min)(bits, digits);
+    RealType R = pow(RealType(2), RealType(engine_bits));
+    RealType mult = R;
+    RealType limit = pow(RealType(2), RealType(b));
+    RealType S = RealType(g() - (g.min)());
+    while(mult < limit) {
+        RealType inc(floor((RealType(g()) - RealType((g.min)())) * R));
+        S += inc * mult;
+        mult *= R;
+    }
+    return S / mult;
+}
+
+}
+
+/**
+ * Returns a value uniformly distributed in the range [0, 1)
+ * with at least @c bits random bits.
+ */
+template<class RealType, std::size_t bits, class URNG>
+RealType generate_canonical(URNG& g)
+{
+    RealType result = detail::generate_canonical_impl<RealType, bits>(
+        g, boost::is_integral<typename URNG::result_type>());
+    BOOST_ASSERT(result >= 0);
+    BOOST_ASSERT(result <= 1);
+    if(result == 1) {
+        result -= std::numeric_limits<RealType>::epsilon() / 2;
+        BOOST_ASSERT(result != 1);
+    }
+    return result;
+}
+
+} // namespace random
+} // namespace boost
+
+#endif // BOOST_RANDOM_GENERATE_CANONICAL_HPP