re PR libstdc++/48114 ([C++0x] binomial_distribution incorrect for p > .5 and geometr...

2011-03-14  Andrey Zholos  <aaz@althenia.net>

	PR libstdc++/48114
	* include/bits/random.h (geometric_distribution): Correct formula
	in comment, per C++0x.
	(geometric_distribution<>::param_type::param_type(double)): Fix check.
	(geometric_distribution<>::param_type::_M_initialize):
	Store log(1 - p).
	* include/bits/random.tcc (geometric_distribution<>::operator()):
	Fix computation.
	(binomial_distribution<>::operator()): Likewise.

From-SVN: r170946

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 6c3f1d34cda58cd698ea2664758b19a5e346e183..ef93431bf09d7fa26f71091d9efe843387bb50ba 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,15 @@
+2011-03-14  Andrey Zholos  <aaz@althenia.net>
+
+       PR libstdc++/48114
+       * include/bits/random.h (geometric_distribution): Correct formula
+       in comment, per C++0x.
+       (geometric_distribution<>::param_type::param_type(double)): Fix check.
+       (geometric_distribution<>::param_type::_M_initialize):
+       Store log(1 - p).
+       * include/bits/random.tcc (geometric_distribution<>::operator()):
+       Fix computation.
+       (binomial_distribution<>::operator()): Likewise.
+
 2011-03-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
        * testsuite/util/testsuite_rvalref.h: Minor tweaks.

diff --git a/libstdc++-v3/include/bits/random.h b/libstdc++-v3/include/bits/random.h
index 5c406a648c34388a138dc76be4660ce4c198537a..26cec8a885e4cf8124ed53e9a47ce0f73a4867a8 100644 (file)
--- a/libstdc++-v3/include/bits/random.h
+++ b/libstdc++-v3/include/bits/random.h
@@ -1,6 +1,6 @@
 // random number generation -*- C++ -*-
 
-// Copyright (C) 2009, 2010 Free Software Foundation, Inc.
+// Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
 // software; you can redistribute it and/or modify it under the
@@ -3589,7 +3589,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    * @brief A discrete geometric random number distribution.
    *
    * The formula for the geometric probability density function is
-   * @f$p(i|p) = (1 - p)p^{i-1}@f$ where @f$p@f$ is the parameter of the
+   * @f$p(i|p) = p(1 - p)^{i}@f$ where @f$p@f$ is the parameter of the
    * distribution.
    */
   template<typename _IntType = int>
@@ -3611,8 +3611,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        param_type(double __p = 0.5)
        : _M_p(__p)
        {
-         _GLIBCXX_DEBUG_ASSERT((_M_p >= 0.0)
-                            && (_M_p <= 1.0));
+         _GLIBCXX_DEBUG_ASSERT((_M_p > 0.0)
+                            && (_M_p < 1.0));
          _M_initialize();
        }
 
@@ -3627,11 +3627,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       private:
        void
        _M_initialize()
-       { _M_log_p = std::log(_M_p); }
+       { _M_log_1_p = std::log(1.0 - _M_p); }
 
        double _M_p;
 
-       double _M_log_p;
+       double _M_log_1_p;
       };
 
       // constructors and member function

diff --git a/libstdc++-v3/include/bits/random.tcc b/libstdc++-v3/include/bits/random.tcc
index 20f7667e2989f53c78aaad155435064d64ef6098..4b17e914e5650c8a7cb07744322fab1f920b0e1b 100644 (file)
--- a/libstdc++-v3/include/bits/random.tcc
+++ b/libstdc++-v3/include/bits/random.tcc
@@ -1025,7 +1025,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
        double __cand;
        do
-         __cand = std::ceil(std::log(__aurng()) / __param._M_log_p);
+         __cand = std::floor(std::log(__aurng()) / __param._M_log_1_p);
        while (__cand >= __thr);
 
        return result_type(__cand + __naf);
@@ -1434,7 +1434,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
        result_type __ret;
        const _IntType __t = __param.t();
-       const _IntType __p = __param.p();
+       const double __p = __param.p();
        const double __p12 = __p <= 0.5 ? __p : 1.0 - __p;
        __detail::_Adaptor<_UniformRandomNumberGenerator, double>
          __aurng(__urng);