Re: [PATCH] libstdc++: add uniform on sphere distribution

[Paolo Carlini]

... fixed with the below.

Thanks,
Paolo.

//////////////////////

2014-08-13  Paolo Carlini  <paolo.carl...@oracle.com>

        PR libstdc++/62118
        * include/ext/random.tcc (uniform_on_sphere_helper<2, _RealType>::
        operator()): Use std::hypot only when _GLIBCXX_USE_C99_MATH_TR1.

Index: include/ext/random.tcc
===================================================================
--- include/ext/random.tcc      (revision 213898)
+++ include/ext/random.tcc      (working copy)
@@ -1547,10 +1547,12 @@
     template<std::size_t _Dimen, typename _RealType>
       class uniform_on_sphere_helper
       {
-       typedef typename uniform_on_sphere_distribution<_Dimen, 
_RealType>::result_type result_type;
+       typedef typename uniform_on_sphere_distribution<_Dimen, _RealType>::
+         result_type result_type;
 
       public:
-       template<typename _NormalDistribution, typename 
_UniformRandomNumberGenerator>
+       template<typename _NormalDistribution,
+                typename _UniformRandomNumberGenerator>
        result_type operator()(_NormalDistribution& __nd,
                               _UniformRandomNumberGenerator& __urng)
         {
@@ -1604,9 +1606,13 @@
            }
          while (__sq == _RealType(0) || __sq > _RealType(1));
 
+#if _GLIBCXX_USE_C99_MATH_TR1
          // Yes, we do not just use sqrt(__sq) because hypot() is more
          // accurate.
          auto __norm = std::hypot(__ret[0], __ret[1]);
+#else
+         auto __norm = std::sqrt(__ret[0] * __ret[0] + __ret[1] * __ret[1]);
+#endif
          __ret[0] /= __norm;
          __ret[1] /= __norm;