/* nag_inteq_volterra_weights (d05bwc) Example Program.
 *
 * Copyright 2011, Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */
#include <nag.h>
#include <nag_stdlib.h>
#include <nagd05.h>

int main(void)
{
  /* Scalars */
  Integer exit_status = 0;
  Integer i, iorder, j, nomg, p, n;
  char    methodstring[10];
  /* Arrays */
  double  *omega = 0, *sw = 0;
  /* NAG types */
  NagError fail;
  Nag_ODEMethod method;

  INIT_FAIL(fail);

  printf("nag_inteq_volterra_weights (d05bwc) Example Program Results\n");

  /* Skip heading in data file*/
  scanf("%*[^\n] ");
  scanf("%s%*[^\n] ", methodstring);

  /*
   * nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value.
   */
  method = (Nag_ODEMethod) nag_enum_name_to_value(methodstring);

  scanf("%ld%*[^\n] ", &iorder);
  scanf("%ld%*[^\n] ", &nomg);

  switch (method)
    {
    case Nag_Adams:
      p = iorder - 1;
      break;
    case Nag_BDF:
      p = iorder;
      break;
    }

  n = nomg + p - 1;

  if (
      !(omega = NAG_ALLOC(nomg, double)) ||
      !(sw = NAG_ALLOC(p*n, double))
      )
    {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  /*
    nag_inteq_volterra_weights (d05bwc).
    Generate weights for use in solving Volterra equations.
  */
  nag_inteq_volterra_weights(method, iorder, nomg, omega, sw, &fail);

  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_inteq_volterra_weights (d05bwc).\n%s\n",
             fail.message);
      exit_status = 1;
      goto END;
    }

  printf("\nThe convolution weights\n\n  n-j        omega\n");
  for (j = 0; j < nomg; j++)
    printf("%3ld     %10.4f\n", j+1, omega[j]);

  printf("\nThe weights W\n");
  printf("\n  i ");
  for (j = 0; j < p; j++)
    printf("%11s%ld ","j = ",j);
  printf("\n");

#define SW(I, J) sw[J * n + I]

  for (i = 0; i < n; i++)
    {
      printf("%3ld", i+1);
      for (j = 0; j < p; j++) printf("%13.4f", SW(i, j));
      printf("\n");
    }

#undef SW

 END:

  if (sw) NAG_FREE(sw);
  if (omega) NAG_FREE(omega);

  return exit_status;
}