/* nag_rand_field_1d_user_setup (g05zmc) Example Program.
 *
 * Copyright 2014 Numerical Algorithms Group.
 *
 * Mark 24, 2013.
 */
#include <math.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagg05.h>
#include <nagx04.h>

#ifdef __cplusplus
extern "C" {
#endif
static void NAG_CALL cov1(double x, double *gamma, Nag_Comm *comm);
#ifdef __cplusplus
}
#endif
static void read_input_data(double *l, double *nu, double *var, double *xmin,
                            double *xmax, Integer *ns, Integer *maxm,
                            Nag_EmbedScale *corr, Nag_EmbedPad *pad);
static void display_results(Integer approx, Integer m, double rho,
                            double *eig, Integer icount, double *lam);
int main(void)
{
  Integer        exit_status = 0;
  /* Scalars */
  double         c, nu, rho, var, xmax, xmin;
  Integer        approx, icount, m, maxm, ns;
  /* Arrays */
  double         eig[3], *lam = 0, *xx = 0;
  /* Nag types */
  Nag_EmbedScale corr;
  Nag_EmbedPad   pad;
  Nag_Comm       comm;
  NagError       fail;

  INIT_FAIL(fail);

  printf("nag_rand_field_1d_user_setup (g05zmc) Example Program Results\n\n");

  /* Get problem specifications from data file*/
  read_input_data(&c, &nu, &var, &xmin, &xmax, &ns, &maxm, &corr, &pad);
  if (!(lam = NAG_ALLOC(maxm, double))||
      !(xx = NAG_ALLOC(ns, double)) ||
      !(comm.user = NAG_ALLOC(2, double)))
    {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  /* Put covariance parameters in communication array*/
  comm.user[0] = c;
  comm.user[1] = nu;
  /* Get square roots of the eigenvalues of the embedding matrix. These are
   * obtained from the setup for simulating one-dimensional random fields,
   * with a user-defined variogram, by the circulant embedding method using
   * nag_rand_field_1d_user_setup (g05zmc).
   */ 
  nag_rand_field_1d_user_setup(ns, xmin, xmax, maxm, var, cov1, pad,
                               corr, lam, xx, &m, &approx, &rho, &icount,
                               eig, &comm, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_rand_field_1d_user_setup (g05zmc).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
  /* Output results*/
  display_results(approx, m, rho, eig, icount, lam);
 END:
  NAG_FREE(lam);
  NAG_FREE(xx);
  NAG_FREE(comm.user);
  return exit_status;
}

void read_input_data(double *l, double *nu, double *var, double *xmin,
                     double *xmax, Integer *ns, Integer *maxm,
                     Nag_EmbedScale *corr, Nag_EmbedPad *pad)
{
  /* Arrays */
  char           nag_enum_arg[40];
   /* Skip heading and get l and nu for cov1 function. */
  scanf("%*[^\n] %lf %lf%*[^\n]",l,nu);
  /* Read in variance of random field. */
  scanf("%lf%*[^\n]",var);
  /* Read in domain endpoints. */
  scanf("%lf %lf%*[^\n]",xmin,xmax);
  /* Read in number of sample points. */
  scanf("%ld%*[^\n]",ns);
  /* Read in maximum size of embedding matrix. */
  scanf("%ld%*[^\n]",maxm);
  /* Read in choice of scaling in case of approximation. */
  scanf(" %39s%*[^\n]", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  *corr = (Nag_EmbedScale) nag_enum_name_to_value(nag_enum_arg);
  /* Read in choice of padding and convert to enum name to value. */
  scanf(" %39s%*[^\n]", nag_enum_arg);
  *pad = (Nag_EmbedPad) nag_enum_name_to_value(nag_enum_arg);
}

void display_results(Integer approx, Integer m, double rho, double *eig,
                     Integer icount, double *lam)
{
  Integer j;
  /* Display size of embedding matrix*/
  printf("\nSize of embedding matrix = %ld\n\n", m);
  /* Display approximation information if approximation used*/
  if (approx==1) {
    printf("Approximation required\n\n");
    printf("rho = %10.5f\n", rho);
    printf("eig = ");
    for (j=0; j<3; j++)
      printf("%10.5f ", eig[j]);
    printf("\nicount = %ld\n", icount);
  } else {
    printf("Approximation not required\n");
  }
  /* Display square roots of the eigenvalues of the embedding matrix*/
  printf("\nSquare roots of eigenvalues of embedding matrix:\n\n");
  for (j=0; j<m; j++) 
    printf("%10.5f%s", lam[j], j%4==3?"\n":"");
  printf("\n");
}

static void NAG_CALL cov1(double x, double *gamma, Nag_Comm *comm)
{
  /* Scalars */
  double    dummy, l, nu;

  /* Correlation length and exponent in comm->ruser.*/
  l = comm->user[0];
  nu = comm->user[1];
  if (x==0.0) {
    *gamma = 1.0;
  } else {
    dummy =  pow(x/l,  nu);
    *gamma = exp(-dummy);
  }
}