/* nag_real_cholesky (f03aec) Example Program.
 *
 * Copyright 1990 Numerical Algorithms Group.
 *
 * Mark 1, 1990.
 * Mark 8 revised, 2004.
 */

#include <nag.h>
#include <math.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nagf03.h>

#define A(I, J) a[(I) *tda + J]

int main(void)
{
  Integer  dete, exit_status = 0, i, j, n, tda;
  NagError fail;
  double   *a = 0, determ, detf, *p = 0;

  INIT_FAIL(fail);

  printf("nag_real_cholesky (f03aec) Example Program Results\n");
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "\n", &n);
  if (n >= 1)
    {
      if (!(a = NAG_ALLOC(n*n, double)) ||
          !(p = NAG_ALLOC(n, double)))
        {
          printf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
      tda = n;
    }
  else
    {
      printf("Invalid n.\n");
      exit_status = 1;
      return exit_status;
    }
  for (i = 0; i < n; i++)
    for (j = 0; j < n; j++)
      scanf("%lf", &A(i, j));
  /* nag_real_cholesky (f03aec).
   * LL^T factorization and determinant of real symmetric
   * positive-definite matrix
   */
  nag_real_cholesky(n, a, tda, p, &detf, &dete, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_real_cholesky (f03aec).\n%s\n",
             fail.message);
      exit_status = 1;
      goto END;
    }
  printf("Array A after factorization\n");
  for (i = 0; i < n; i++)
    for (j = 0; j < n; j++)
      printf("%9.4f%s", A(i, j), (j%8 == 7 || j == n-1)?"\n":" ");
  printf("\nArray p\n");
  for (i = 0; i < n; i++)
    printf("%9.4f%s", p[i], (i%8 == 7 || i == n-1)?"\n":" ");
  printf("\ndetf = %9.4f           dete = %2" NAG_IFMT "\n\n", detf, dete);
  determ = detf*pow(2.0, (double) dete);
  printf("Value of determinant = %9.4f\n", determ);
 END:
  if (a) NAG_FREE(a);
  if (p) NAG_FREE(p);
  return exit_status;
}