/* nag_nd_shep_eval (e01znc) Example Program.
 *
 * Copyright 2014 Numerical Algorithms Group.
 *
 * Mark 24, 2013.
 */
#include <math.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nage01.h>
#include <nagg05.h>

static double funct(double *x);

int main(void)
{
  /* Scalars */
  Integer     d = 6, exit_status = 0, lseed = 1, subid = 0;
  Integer     i, j, liq, lrq, lstate, m, n, nq, nw, tmpdsm;
  double      fun;
  /* Arrays */
  double      *f = 0, *q = 0, *qx = 0, *rq = 0, *x = 0, *xe = 0;
  Integer     *iq = 0, *state = 0;
  Integer     seed[] = { 1762543 };
  /* Nag Types */
  Nag_BaseRNG genid = Nag_Basic;
  NagError    fail;

  INIT_FAIL(fail);

  printf("nag_nd_shep_eval (e01znc) Example Program Results\n\n");
  /* Skip heading in data file*/
  scanf("%*[^\n] ");
  /* Set up state array for generating a random sample of data locations
   * using nag_rand_init_repeatable (g05kfc).
   *
   * First get the length of the state array by setting lstate = -1.
   */
  lstate = -1;
  nag_rand_init_repeatable(genid, subid, seed, lseed, state, &lstate, &fail);
  if (fail.code == NE_NOERROR)
    {
      /* Allocate arrays */
      if (!(state = NAG_ALLOC(lstate, Integer)))
        {
          printf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }

      /* Then initialise the generator to a repeatable sequence */
      nag_rand_init_repeatable(genid, subid, seed, lseed, state, &lstate,
                               &fail);
    }
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_rand_init_repeatable (g05kfc).\n%s\n",
             fail.message);
      exit_status = 1;
      goto END;
    }

  /* Input the number of nodes.*/
  scanf("%ld%*[^\n] ", &m);
  liq = 2 * m + 1;
  lrq = (d + 1) * (d + 2)/2 * m + 2 * d + 1;
  if (
    !(x = NAG_ALLOC(d*m, double)) ||
    !(f = NAG_ALLOC(m, double)) ||
    !(iq = NAG_ALLOC(liq, Integer)) ||
    !(rq = NAG_ALLOC(lrq, double))
    )
    {
      printf("Allocation failure\n");
      exit_status = -2;
      goto END;
    }
  /* Generate d*m  pseudorandom numbers in U(0,1) using
   * nag_rand_basic (g05sac).
   */
  tmpdsm = d*m;
  nag_rand_basic(tmpdsm, state, x, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_rand_basic (g05sac).\n%s\n", fail.message);
      exit_status = 2;
      goto END;
    }

  /* Evaluate f at x */
  for (i = 0; i < m; i++)
    f[i] = funct(&x[i*d]);

  /* Generate the interpolant using nag_nd_shep_interp (e01zmc):
     Interpolating functions, modified Shepard's method, d variables.
   */
  nq = 0;
  nw = 0;
  nag_nd_shep_interp(d, m, x, f, nw, nq, iq, rq, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_nd_shep_interp (e01zmc).\n%s\n", fail.message);
      exit_status = 3;
      goto END;
    }

  /* Input the number of evaluation points and allocate arrays with lengths
     based on this.
   */
  scanf("%ld%*[^\n]", &n);
  if (
    !(xe = NAG_ALLOC(d*n, double)) ||
    !(q = NAG_ALLOC(n, double)) ||
    !(qx = NAG_ALLOC(d*n, double))
    )
    {
      printf("Allocation failure\n");
      exit_status = -3;
      goto END;
    }

  /* Generate a set of evaluation points lying on diagonal line
   * xe(1:d,i) = xe(1,i) = i/(n+1).
   */
  for (i = 0; i < n; i++)
    for (j = 0; j < d; j++)
      xe[i*d+j] = (double) (i+1)/(double) (n + 1);

  /* Evaluate the interpolant using nag_nd_shep_eval (e01znc), at given
     interpolated values, where interpolant previously computed by e01zmc.
   */
  nag_nd_shep_eval(d, m, x, f, iq, rq, n, xe, q, qx, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_nd_shep_eval (e01znc).\n%s\n", fail.message);
      exit_status = 4;
      goto END;
    }

  /* Print interpolated function values against actual function values
   * at the points on the diagonal line. */
  /* Header */
  printf("    i  |  f(i)      q(i)    | |f(i)-q(i)|\n");
  printf("    ---|--------------------+---------------\n");
  /* Results */
  for (i = 0; i < n; i++)
    {
      fun = funct(&xe[i*d]);
      printf("%5ld %10.4f%10.4f%10.4f\n", i, fun, q[i], fabs(fun-q[i]));
    }

 END:

  NAG_FREE(f);
  NAG_FREE(q);
  NAG_FREE(qx);
  NAG_FREE(rq);
  NAG_FREE(x);
  NAG_FREE(xe);
  NAG_FREE(iq);
  NAG_FREE(state);

  return exit_status;
}
static double funct(double *x)
{
  double funct_return;
  funct_return = x[0]*x[1]*x[2]/(1.0 + 2.0*x[3]*x[4]*x[5]);
  return funct_return;
}