GroovX: src/mtx/mathspecial.h Source File

00001 
00004 
00005 //
00006 // Copyright (c) 2001-2004 California Institute of Technology
00007 // Copyright (c) 2004-2007 University of Southern California
00008 // Rob Peters <rjpeters at usc dot edu>
00009 //
00010 // created: Thu Mar  8 16:27:36 2001 (split from num.h)
00011 // commit: $Id: mathspecial.h 10065 2007-04-12 05:54:56Z rjpeters $
00012 // $HeadURL: file:///lab/rjpeters/svnrepo/code/trunk/groovx/src/mtx/mathspecial.h $
00013 //
00014 // --------------------------------------------------------------------
00015 //
00016 // This file is part of GroovX.
00017 //   [http://ilab.usc.edu/rjpeters/groovx/]
00018 //
00019 // GroovX is free software; you can redistribute it and/or modify it
00020 // under the terms of the GNU General Public License as published by
00021 // the Free Software Foundation; either version 2 of the License, or
00022 // (at your option) any later version.
00023 //
00024 // GroovX is distributed in the hope that it will be useful, but
00025 // WITHOUT ANY WARRANTY; without even the implied warranty of
00026 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00027 // General Public License for more details.
00028 //
00029 // You should have received a copy of the GNU General Public License
00030 // along with GroovX; if not, write to the Free Software Foundation,
00031 // Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
00032 //
00034 
00035 #ifndef GROOVX_PKGS_MTX_MATHSPECIAL_H_UTC20050626084022_DEFINED
00036 #define GROOVX_PKGS_MTX_MATHSPECIAL_H_UTC20050626084022_DEFINED
00037 
00038 #include <cmath>
00039 
00041 namespace dash
00042 {
00043   namespace detail
00044   {
00045     double gammaln_engine(double xx);
00046   }
00047 
00049   inline double gammaln(double xx)
00050   {
00051     static bool filled = false;
00052     static const int TABLE_SIZE = 101;
00053     static double lookup[TABLE_SIZE] = { 0.0 };
00054 
00055 
00056     const double tol = 1e-50;
00057 
00058     const int ival = int(xx);
00059 
00060     if ( (ival < TABLE_SIZE) && (xx - double(ival) < tol) )
00061       {
00062         if (!filled)
00063           {
00064             for (int i = 0; i < TABLE_SIZE; ++i)
00065               lookup[i] = dash::detail::gammaln_engine(double(i));
00066 
00067             filled = true;
00068           }
00069         return lookup[ival];
00070       }
00071     else
00072       {
00073         return dash::detail::gammaln_engine(xx);
00074       }
00075   }
00076 
00078   inline double erfc(const double x)
00079   {
00080     const double z = fabs(x);
00081 
00082     const double t = 1.0/(1.0+0.5*fabs(x));
00083 
00084     const double ans =
00085       t*exp(-z*z-1.26551223+t*(1.00002368+t*(0.37409196+t*(0.09678418+
00086       t*(-0.18628806+t*(0.27886807+t*(-1.13520398+t*(1.48851587+
00087       t*(-0.82215223+t*0.17087277)))))))))
00088       ;
00089 
00090     return x >= 0.0 ? ans : 2.0-ans;
00091   }
00092 }
00093 
00094 static const char __attribute__((used)) vcid_groovx_pkgs_mtx_mathspecial_h_utc20050626084022[] = "$Id: mathspecial.h 10065 2007-04-12 05:54:56Z rjpeters $ $HeadURL: file:
00095 #endif // !GROOVX_PKGS_MTX_MATHSPECIAL_H_UTC20050626084022_DEFINED