src/gromacs/gmxana/polynomials.c

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  37 #include "config.h"
  38
  39 #include <stdio.h>
  40 #include <math.h>
  41 #include "typedefs.h"
  42 #include "gromacs/utility/fatalerror.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     {
  52         case eacP0:
  53             polynomial = 1.0;
  54             break;
  55         case eacP1:
  56             polynomial = x;
  57             break;
  58         case eacP2:
  59             x2         = x*x;
  60             polynomial = 1.5*x2 - 0.5;
  61             break;
  62         case eacP3:
  63             x2         = x*x;
  64             polynomial = (35*x2*x2 - 30*x2 + 3)/8;
  65             break;
  66         case eacP4:
  67             x2         = x*x;
  68             x3         = x2*x;
  69             polynomial = (63*x3*x2 - 70*x3 + 15*x)/8;
  70             break;
  71         default:
  72             gmx_fatal(FARGS, "Legendre polynomials of order %d are not supported, %s %d",
  73                       m, __FILE__, __LINE__);
  74     }
  75     return (polynomial);
  76 }