Fix and optimize von_mises_distribution class.

From-SVN: r196436

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index cbba5e21e29b7745c6fa05407f5d080f7e0a9ace..4068530f8f522a9026af04a0306c6962e0f7c6cf 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2013-03-04  Ulrich Drepper  <drepper@gmail.com>
+
+       * include/ext/random (__gnu_cxx::von_mises_distribution<>):
+       Optimize generation function by pulling computation of __r into the
+       constructor for param_type.  Also compare _M_mu in operator==.
+       Fix comment.
+
 2013-03-02  Ulrich Drepper  <drepper@gmail.com>
 
        Add triangular and von Mises distributions.

diff --git a/libstdc++-v3/include/ext/random b/libstdc++-v3/include/ext/random
index 51d332b4c401483c0e2140f3511f438927d10ace..7af3130087e7926cf07057bb2cec35ff2a6bcee3 100644 (file)
--- a/libstdc++-v3/include/ext/random
+++ b/libstdc++-v3/include/ext/random
@@ -2621,6 +2621,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
          const _RealType __pi = __gnu_cxx::__math_constants<_RealType>::__pi;
          _GLIBCXX_DEBUG_ASSERT(_M_mu >= -__pi && _M_mu <= __pi);
          _GLIBCXX_DEBUG_ASSERT(_M_kappa >= _RealType(0));
+
+         auto __tau = std::sqrt(_RealType(4) * _M_kappa * _M_kappa
+                                + _RealType(1)) + _RealType(1);
+         auto __rho = ((__tau - std::sqrt(_RealType(2) * __tau))
+                       / (_RealType(2) * _M_kappa));
+         _M_r = (_RealType(1) + __rho * __rho) / (_RealType(2) * __rho);
        }
 
        _RealType
@@ -2633,16 +2639,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
        friend bool
        operator==(const param_type& __p1, const param_type& __p2)
-       { return __p1._M_kappa == __p2._M_kappa; }
+       { return (__p1._M_mu == __p2._M_mu
+                 && __p1._M_kappa == __p2._M_kappa); }
 
       private:
-
        _RealType _M_mu;
        _RealType _M_kappa;
+       _RealType _M_r;
       };
 
       /**
-       * @brief Constructs a beta distribution with parameters
+       * @brief Constructs a von Mises distribution with parameters
        * @f$\mu@f$ and @f$\kappa@f$.
        */
       explicit
@@ -2727,20 +2734,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            = __gnu_cxx::__math_constants<result_type>::__pi;
          std::__detail::_Adaptor<_UniformRandomNumberGenerator, result_type>
            __aurng(__urng);
-         result_type __tau = (std::sqrt(result_type(4) * this->kappa()
-                                        * this->kappa() + result_type(1))
-                              + result_type(1));
-         result_type __rho = ((__tau - std::sqrt(result_type(2) * __tau))
-                              / (result_type(2) * this->kappa()));
-         result_type __r = ((result_type(1) + __rho * __rho)
-                            / (result_type(2) * __rho));
 
          result_type __f;
          while (1)
            {
              result_type __rnd = std::cos(__pi * __aurng());
-             __f = (result_type(1) + __r * __rnd) / (__r + __rnd);
-             result_type __c = this->kappa() * (__r - __f);
+             __f = (result_type(1) + __p._M_r * __rnd) / (__p._M_r + __rnd);
+             result_type __c = __p._M_kappa * (__p._M_r - __f);
 
              result_type __rnd2 = __aurng();
              if (__c * (result_type(2) - __c) > __rnd2)
@@ -2756,7 +2756,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
          if (__aurng() < result_type(0.5))
            __res = -__res;
 #endif
-         __res += this->mu();
+         __res += __p._M_mu;
          if (__res > __pi)
            __res -= result_type(2) * __pi;
          else if (__res < -__pi)