/* nag_inteq_abel2_weak (d05bdc) Example Program.
 *
 * Copyright 2011, Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */
#include <math.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagd05.h>
#include <nagx01.h>
#include <nagx02.h>

#ifdef __cplusplus
extern "C" {
#endif
  static double NAG_CALL ck1(double t, Nag_Comm *comm);
  static double NAG_CALL cf1(double t, Nag_Comm *comm);
  static double NAG_CALL cg1(double s, double y, Nag_Comm *comm);
  static double NAG_CALL ck2(double t, Nag_Comm *comm);
  static double NAG_CALL cf2(double t, Nag_Comm *comm);
  static double NAG_CALL cg2(double s, double y, Nag_Comm *comm);
#ifdef __cplusplus
}
#endif

int main(void)
{
  /* Scalars */
  double  h, t, tlim, tolnl;
  Integer exit_status = 0;
  Integer iorder = 4;
  Integer exno, i, iskip, nmesh, lrwsav;
  /* Arrays */
  double  *rwsav = 0, *yn = 0;
  /* NAG types */
  Nag_Comm comm;
  NagError fail;
  Nag_WeightMode wtmode;

  INIT_FAIL(fail);

  printf("nag_inteq_abel2_weak (d05bdc) Example Program Results\n");

  nmesh = pow(2, 6) + 7;
  lrwsav = (2 * iorder + 6) * nmesh + 8 * pow(iorder, 2) - 16 * iorder + 1;

  if (
      !(yn = NAG_ALLOC(nmesh, double)) ||
      !(rwsav = NAG_ALLOC(lrwsav, double))
      )
    {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  tolnl = sqrt(nag_machine_precision);

  for (exno = 1; exno <= 2; exno++)
    {
      printf("\nExample %ld\n\n", exno);

      if (exno==1)
        {
          tlim = 7.0;
          iskip = 5;
          h = tlim/(double) (nmesh - 1);
          wtmode = Nag_InitWeights;

          /*
            nag_inteq_abel2_weak (d05bdc).
            Nonlinear convolution Volterra-Abel equation, second kind,
            weakly singular.
          */
          nag_inteq_abel2_weak(ck1, cf1, cg1, wtmode, iorder, tlim, tolnl,
                               nmesh, yn, rwsav, lrwsav, &comm, &fail);
        }
      else
        {
          tlim = 5.0;
          iskip = 7;
          h = tlim/(double) (nmesh - 1);
          wtmode = Nag_ReuseWeights;

          /* nag_inteq_abel2_weak (d05bdc) as above. */
          nag_inteq_abel2_weak(ck2, cf2, cg2, wtmode, iorder, tlim, tolnl,
                               nmesh, yn, rwsav, lrwsav, &comm, &fail);
        }
      if (fail.code != NE_NOERROR)
        {
          printf("Error from nag_inteq_abel2_weak (d05bdc).\n%s\n",
                 fail.message);
          exit_status = 1;
          goto END;
        }

      printf("The stepsize h = %8.4f\n\n", h);
      printf("     t        Approximate\n");
      printf("                Solution\n\n");

      for (i = 0; i < nmesh; i++)
        {
          t = (double) (i) * h;
          if (i%iskip == 0) printf("%8.4f%15.4f\n", t, yn[i]);
        }
    }

 END:
  if (rwsav) NAG_FREE(rwsav);
  if (yn) NAG_FREE(yn);

  return exit_status;
}

static double NAG_CALL ck1(double t, Nag_Comm *comm)
{
  return -sqrt(nag_pi);
}
static double NAG_CALL cf1(double t, Nag_Comm *comm)
{
  return sqrt(t) + (3.0 / 8.0) * nag_pi * pow(t, 2);
}
static double NAG_CALL cg1(double s, double y, Nag_Comm *comm)
{
  return pow(y, 3);
}
static double NAG_CALL ck2(double t, Nag_Comm *comm)
{
  return -sqrt(nag_pi);
}
static double NAG_CALL cf2(double t, Nag_Comm *comm)
{
  return (3.0 - t) * sqrt(t);
}
static double NAG_CALL cg2(double s, double y, Nag_Comm *comm)
{
  return exp(s * pow(1.0 - s, 2) - pow(y, 2));
}