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authorBen Cheng <bccheng@google.com>2014-03-25 22:37:19 -0700
committerBen Cheng <bccheng@google.com>2014-03-25 22:37:19 -0700
commit1bc5aee63eb72b341f506ad058502cd0361f0d10 (patch)
treec607e8252f3405424ff15bc2d00aa38dadbb2518 /gcc-4.9/libstdc++-v3/include/tr1/beta_function.tcc
parent283a0bf58fcf333c58a2a92c3ebbc41fb9eb1fdb (diff)
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Initial checkin of GCC 4.9.0 from trunk (r208799).
Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba
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+// Special functions -*- C++ -*-
+
+// Copyright (C) 2006-2014 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.
+//
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file tr1/beta_function.tcc
+ * This is an internal header file, included by other library headers.
+ * Do not attempt to use it directly. @headername{tr1/cmath}
+ */
+
+//
+// ISO C++ 14882 TR1: 5.2 Special functions
+//
+
+// Written by Edward Smith-Rowland based on:
+// (1) Handbook of Mathematical Functions,
+// ed. Milton Abramowitz and Irene A. Stegun,
+// Dover Publications,
+// Section 6, pp. 253-266
+// (2) The Gnu Scientific Library, http://www.gnu.org/software/gsl
+// (3) Numerical Recipes in C, by W. H. Press, S. A. Teukolsky,
+// W. T. Vetterling, B. P. Flannery, Cambridge University Press (1992),
+// 2nd ed, pp. 213-216
+// (4) Gamma, Exploring Euler's Constant, Julian Havil,
+// Princeton, 2003.
+
+#ifndef _GLIBCXX_TR1_BETA_FUNCTION_TCC
+#define _GLIBCXX_TR1_BETA_FUNCTION_TCC 1
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+namespace tr1
+{
+ // [5.2] Special functions
+
+ // Implementation-space details.
+ namespace __detail
+ {
+ _GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+ /**
+ * @brief Return the beta function: \f$B(x,y)\f$.
+ *
+ * The beta function is defined by
+ * @f[
+ * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)}
+ * @f]
+ *
+ * @param __x The first argument of the beta function.
+ * @param __y The second argument of the beta function.
+ * @return The beta function.
+ */
+ template<typename _Tp>
+ _Tp
+ __beta_gamma(_Tp __x, _Tp __y)
+ {
+
+ _Tp __bet;
+#if _GLIBCXX_USE_C99_MATH_TR1
+ if (__x > __y)
+ {
+ __bet = std::tr1::tgamma(__x)
+ / std::tr1::tgamma(__x + __y);
+ __bet *= std::tr1::tgamma(__y);
+ }
+ else
+ {
+ __bet = std::tr1::tgamma(__y)
+ / std::tr1::tgamma(__x + __y);
+ __bet *= std::tr1::tgamma(__x);
+ }
+#else
+ if (__x > __y)
+ {
+ __bet = __gamma(__x) / __gamma(__x + __y);
+ __bet *= __gamma(__y);
+ }
+ else
+ {
+ __bet = __gamma(__y) / __gamma(__x + __y);
+ __bet *= __gamma(__x);
+ }
+#endif
+
+ return __bet;
+ }
+
+ /**
+ * @brief Return the beta function \f$B(x,y)\f$ using
+ * the log gamma functions.
+ *
+ * The beta function is defined by
+ * @f[
+ * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)}
+ * @f]
+ *
+ * @param __x The first argument of the beta function.
+ * @param __y The second argument of the beta function.
+ * @return The beta function.
+ */
+ template<typename _Tp>
+ _Tp
+ __beta_lgamma(_Tp __x, _Tp __y)
+ {
+#if _GLIBCXX_USE_C99_MATH_TR1
+ _Tp __bet = std::tr1::lgamma(__x)
+ + std::tr1::lgamma(__y)
+ - std::tr1::lgamma(__x + __y);
+#else
+ _Tp __bet = __log_gamma(__x)
+ + __log_gamma(__y)
+ - __log_gamma(__x + __y);
+#endif
+ __bet = std::exp(__bet);
+ return __bet;
+ }
+
+
+ /**
+ * @brief Return the beta function \f$B(x,y)\f$ using
+ * the product form.
+ *
+ * The beta function is defined by
+ * @f[
+ * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)}
+ * @f]
+ *
+ * @param __x The first argument of the beta function.
+ * @param __y The second argument of the beta function.
+ * @return The beta function.
+ */
+ template<typename _Tp>
+ _Tp
+ __beta_product(_Tp __x, _Tp __y)
+ {
+
+ _Tp __bet = (__x + __y) / (__x * __y);
+
+ unsigned int __max_iter = 1000000;
+ for (unsigned int __k = 1; __k < __max_iter; ++__k)
+ {
+ _Tp __term = (_Tp(1) + (__x + __y) / __k)
+ / ((_Tp(1) + __x / __k) * (_Tp(1) + __y / __k));
+ __bet *= __term;
+ }
+
+ return __bet;
+ }
+
+
+ /**
+ * @brief Return the beta function \f$ B(x,y) \f$.
+ *
+ * The beta function is defined by
+ * @f[
+ * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)}
+ * @f]
+ *
+ * @param __x The first argument of the beta function.
+ * @param __y The second argument of the beta function.
+ * @return The beta function.
+ */
+ template<typename _Tp>
+ inline _Tp
+ __beta(_Tp __x, _Tp __y)
+ {
+ if (__isnan(__x) || __isnan(__y))
+ return std::numeric_limits<_Tp>::quiet_NaN();
+ else
+ return __beta_lgamma(__x, __y);
+ }
+
+ _GLIBCXX_END_NAMESPACE_VERSION
+ } // namespace std::tr1::__detail
+}
+}
+
+#endif // __GLIBCXX_TR1_BETA_FUNCTION_TCC