/* check_deriv.c check against each other */
#include <stdio.h>
#include <stdlib.h>
#include "deriv.h"
#include "nuderiv.h"

#undef abs
#define abs(x) ((x)<0.0?(-(x)):(x))

int main(int argc, char *argv[])
{
  double cx[100];
  double cxnu[100];
  double xg[100];
  double h, err;
  double maxerr = 0.0;
  int norder = 4;
  int i, j, npoints;
  int imax, jmax;

  printf("check_deriv.c running \n");
  h = 1.0;
  for(npoints=9; npoints<23; npoints++)
  {
    for(i=0; i<npoints; i++)
    {
      xg[i] = h*(double)(i-1);
    }
    j = 1;
    nuderiv(norder, npoints, j, xg, cxnu);
    rderiv(norder, npoints, j, h, cx);
    for(i=0; i<npoints; i++)
    {
      err = abs(cx[i]-cxnu[i]);
      if(err>maxerr) {maxerr = err; imax=i; jmax=j;}
    }
    printf("n=%d, im=%d, x=%f, r=%f, nu=%f, err=%g \n", npoints,
	   imax, xg[imax], cx[imax], cxnu[imax], cx[imax]-cxnu[imax]); 
  }
  printf("check_deriv.c ending \n");
  return 0;
} /* end check_deriv.c */