Here is a patch for
PR libstdc++/68397 std::tr1::expint fails in __expint_En_cont_frac
for some long double arguments due to low __max_iter value.
The proposed resolution of increasing the max_iter to 1000 is a simple
and obvious fix.
Built and tested on x86_64-linux.
OK?
Ed
2017-04-20 Edward Smith-Rowland <3dw...@verizon.net>
PR libstdc++/68397 std::tr1::expint fails ... long double arguments.
* include/tr1/exp_integral.tcc: Increase iteration limits.
* testsuite/tr1/5_numerical_facilities/special_functions/15_expint/
pr68397.cc: New test.
* testsuite/special_functions/14_expint/pr68397.cc: New test.
Index: include/tr1/exp_integral.tcc
===
--- include/tr1/exp_integral.tcc(revision 246797)
+++ include/tr1/exp_integral.tcc(working copy)
@@ -86,7 +86,7 @@
_Tp __term = _Tp(1);
_Tp __esum = _Tp(0);
_Tp __osum = _Tp(0);
- const unsigned int __max_iter = 100;
+ const unsigned int __max_iter = 1000;
for (unsigned int __i = 1; __i < __max_iter; ++__i)
{
__term *= - __x / __i;
@@ -156,7 +156,7 @@
_Tp
__expint_En_series(unsigned int __n, _Tp __x)
{
- const unsigned int __max_iter = 100;
+ const unsigned int __max_iter = 1000;
const _Tp __eps = std::numeric_limits<_Tp>::epsilon();
const int __nm1 = __n - 1;
_Tp __ans = (__nm1 != 0
@@ -202,7 +202,7 @@
_Tp
__expint_En_cont_frac(unsigned int __n, _Tp __x)
{
- const unsigned int __max_iter = 100;
+ const unsigned int __max_iter = 1000;
const _Tp __eps = std::numeric_limits<_Tp>::epsilon();
const _Tp __fp_min = std::numeric_limits<_Tp>::min();
const int __nm1 = __n - 1;
Index:
testsuite/tr1/5_numerical_facilities/special_functions/15_expint/pr68397.cc
===
--- testsuite/tr1/5_numerical_facilities/special_functions/15_expint/pr68397.cc
(nonexistent)
+++ testsuite/tr1/5_numerical_facilities/special_functions/15_expint/pr68397.cc
(working copy)
@@ -0,0 +1,46 @@
+// Copyright (C) 2017 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
+// .
+
+// PR libstdc++/68397 - std::tr1::expint fails in __expint_En_cont_frac
+// for some long double arguments due to low __max_iter value
+
+#include
+#include
+
+void
+test01()
+{
+ // Answers from Wolfram Alpha.
+ long double ans_ok = -0.10001943365331651406888645149537315243646135979573L;
+ long double ans_bomb =
-0.1027809650077516264612749163100483995270163783L;
+
+ long double Ei_ok = std::tr1::expint(-1.51L);
+ long double diff_ok = std::abs(Ei_ok - ans_ok);
+ VERIFY(diff_ok < 1.0e-15L);
+
+ long double Ei_bomb = std::tr1::expint(-1.450001L);
+ long double diff_bomb = std::abs(Ei_bomb - ans_bomb);
+ VERIFY(diff_bomb < 1.0e-15L);
+}
+
+int
+main()
+{
+ test01();
+ return 0;
+}
+
Index: testsuite/special_functions/14_expint/pr68397.cc
===
--- testsuite/special_functions/14_expint/pr68397.cc(nonexistent)
+++ testsuite/special_functions/14_expint/pr68397.cc(working copy)
@@ -0,0 +1,47 @@
+// { dg-do run { target c++11 } }
+// { dg-options "-D__STDCPP_WANT_MATH_SPEC_FUNCS__" }
+// Copyright (C) 2017 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
+// .
+
+// PR libstdc++/68397 - std::tr1::expint fails in __expint_En_cont_frac
+// for some long double arguments due to low __max_iter value
+
+#include
+#include
+
+int
+test01
