2011-11-02 Richard B. Kreckel <kreckel@ginac.de>

	    Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/50880
	* include/std/complex (__complex_acosh): Fix in a better way,
	use Kahan's formula.
	* include/tr1/complex (__complex_acosh): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_6-branch@180804 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index a2b34f5..99bde20 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,20 @@
+2011-11-02  Richard B. Kreckel  <kreckel@ginac.de>
+           Paolo Carlini  <paolo.carlini@oracle.com>
+
+       PR libstdc++/50880
+       * include/std/complex (__complex_acosh): Fix in a better way,
+       use Kahan's formula.
+       * include/tr1/complex (__complex_acosh): Likewise.
+
+2011-11-02  Richard B. Kreckel  <kreckel@ginac.de>
+           Paolo Carlini  <paolo.carlini@oracle.com>
+
+       PR libstdc++/50880
+       * include/std/complex (__complex_acosh): Fix for __z.real() < 0.
+       * include/tr1/complex (__complex_acosh): Likewise.
+       * testsuite/26_numerics/complex/50880.cc: New.
+       * testsuite/tr1/8_c_compatibility/complex/50880.cc: Likewise.
+
 2011-10-26  Release Manager
 
        * GCC 4.6.2 released.

diff --git a/libstdc++-v3/include/std/complex b/libstdc++-v3/include/std/complex
index aa6e81d..da3c469 100644 (file)
--- a/libstdc++-v3/include/std/complex
+++ b/libstdc++-v3/include/std/complex
@@ -1,7 +1,7 @@
 // The template and inlines for the -*- C++ -*- complex number classes.
 
 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
-// 2006, 2007, 2008, 2009, 2010
+// 2006, 2007, 2008, 2009, 2010, 2011
 // Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
@@ -1695,12 +1695,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     std::complex<_Tp>
     __complex_acosh(const std::complex<_Tp>& __z)
     {
-      std::complex<_Tp> __t((__z.real() - __z.imag())
-                           * (__z.real() + __z.imag()) - _Tp(1.0),
-                           _Tp(2.0) * __z.real() * __z.imag());
-      __t = std::sqrt(__t);
-
-      return std::log(__t + __z);
+      // Kahan's formula.
+      return _Tp(2.0) * std::log(std::sqrt(_Tp(0.5) * (__z + _Tp(1.0)))
+                                + std::sqrt(_Tp(0.5) * (__z - _Tp(1.0))));
     }
 
 #if _GLIBCXX_USE_C99_COMPLEX_TR1

diff --git a/libstdc++-v3/include/tr1/complex b/libstdc++-v3/include/tr1/complex
index fc213b8..689ea16 100644 (file)
--- a/libstdc++-v3/include/tr1/complex
+++ b/libstdc++-v3/include/tr1/complex
@@ -185,12 +185,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     std::complex<_Tp>
     __complex_acosh(const std::complex<_Tp>& __z)
     {
-      std::complex<_Tp> __t((__z.real() - __z.imag())
-                           * (__z.real() + __z.imag()) - _Tp(1.0),
-                           _Tp(2.0) * __z.real() * __z.imag());
-      __t = std::sqrt(__t);
-
-      return std::log(__t + __z);
+      // Kahan's formula.
+      return _Tp(2.0) * std::log(std::sqrt(_Tp(0.5) * (__z + _Tp(1.0)))
+                                + std::sqrt(_Tp(0.5) * (__z - _Tp(1.0))));
     }
 
 #if _GLIBCXX_USE_C99_COMPLEX_TR1

diff --git a/libstdc++-v3/testsuite/26_numerics/complex/50880.cc b/libstdc++-v3/testsuite/26_numerics/complex/50880.cc
new file mode 100644 (file)
index 0000000..2b70a99
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/complex/50880.cc
@@ -0,0 +1,53 @@
+// { dg-options "-std=gnu++0x" }
+//
+// Copyright (C) 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
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <complex>
+#include <testsuite_hooks.h> 
+
+template<typename T>
+  void test01_do()
+  {
+    bool test __attribute__((unused)) = true;
+
+    const std::complex<T> ca(T(-2), T(2));
+    const std::complex<T> cb(T(-2), T(0));
+    const std::complex<T> cc(T(-2), T(-2));
+
+    std::complex<T> cra = std::acosh(ca);
+    std::complex<T> crb = std::acosh(cb);
+    std::complex<T> crc = std::acosh(cc);
+
+    VERIFY( cra.real() > T(0) );
+    VERIFY( crb.real() > T(0) );
+    VERIFY( crc.real() > T(0) );
+  }
+
+// libstdc++/50880
+void test01()
+{
+  test01_do<float>();
+  test01_do<double>();
+  test01_do<long double>();
+}
+
+int main()
+{
+  test01();
+  return 0;
+}

diff --git a/libstdc++-v3/testsuite/tr1/8_c_compatibility/complex/50880.cc b/libstdc++-v3/testsuite/tr1/8_c_compatibility/complex/50880.cc
new file mode 100644 (file)
index 0000000..eaa2f3d
--- /dev/null
+++ b/libstdc++-v3/testsuite/tr1/8_c_compatibility/complex/50880.cc
@@ -0,0 +1,51 @@
+// Copyright (C) 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
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <tr1/complex>
+#include <testsuite_hooks.h> 
+
+template<typename T>
+  void test01_do()
+  {
+    bool test __attribute__((unused)) = true;
+
+    const std::complex<T> ca(T(-2), T(2));
+    const std::complex<T> cb(T(-2), T(0));
+    const std::complex<T> cc(T(-2), T(-2));
+
+    std::complex<T> cra = std::tr1::acosh(ca);
+    std::complex<T> crb = std::tr1::acosh(cb);
+    std::complex<T> crc = std::tr1::acosh(cc);
+
+    VERIFY( cra.real() > T(0) );
+    VERIFY( crb.real() > T(0) );
+    VERIFY( crc.real() > T(0) );
+  }
+
+// libstdc++/50880
+void test01()
+{
+  test01_do<float>();
+  test01_do<double>();
+  test01_do<long double>();
+}
+
+int main()
+{
+  test01();
+  return 0;
+}