src/tools/polynomials.c

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  35 #ifdef HAVE_CONFIG_H
  36 #include <config.h>
  37 #endif
  38
  39 #include <stdio.h>
  40 #include <math.h>
  41 #include "typedefs.h"
  42 #include "gmx_fatal.h"
  43 #include "gstat.h"
  44
  45 real LegendreP(real x,unsigned long m)
  46
  47 {
  48   real polynomial=0,x2,x3;
  49
  50   switch (m) {
  51   case eacP0:
  52     polynomial=1.0;
  53     break;
  54   case eacP1:
  55     polynomial=x;
  56     break;
  57   case eacP2:
  58     x2=x*x;
  59     polynomial=1.5*x2 - 0.5;
  60     break;
  61   case eacP3:
  62     x2=x*x;
  63     polynomial=(35*x2*x2 - 30*x2 + 3)/8;
  64     break;
  65   case eacP4:
  66     x2=x*x;
  67     x3=x2*x;
  68     polynomial=(63*x3*x2 - 70*x3 + 15*x)/8;
  69     break;
  70   default:
  71     gmx_fatal(FARGS,"Legendre polynomials of order %d are not supported, %s %d",
  72                 m,__FILE__,__LINE__);
  73   }
  74   return (polynomial);
  75 }