/* nag_real_cholesky_skyline (f01mcc) Example Program.
 *
 * Copyright 1996 Numerical Algorithms Group.
 *
 * Mark 4, 1996.
 * Mark 8 revised, 2004.
 */

#include <nag.h>
#include <nagx04.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nagf01.h>

int main(int argc, char *argv[])
{
  FILE     *fpin, *fpout;
  Integer  exit_status = 0, i, k, k1, k2, lal, n, *row = 0;
  NagError fail;
  double   *a = 0, *al = 0, *d = 0;

  INIT_FAIL(fail);

  /* Check for command-line IO options */
  fpin = nag_example_file_io(argc, argv, "-data", NULL);
  fpout = nag_example_file_io(argc, argv, "-results", NULL);
  fprintf(fpout,
          "nag_real_cholesky_skyline (f01mcc) Example Program Results\n");
  /* Skip heading in data file */
  fscanf(fpin, "%*[^\n]");
  fscanf(fpin, "%ld", &n);
  if (n >= 1)
    {
      if (!(row = NAG_ALLOC(n, Integer)) ||
          !(d = NAG_ALLOC(n, double)))
        {
          fprintf(fpout, "Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      fprintf(fpout, "Invalid n.\n");
      exit_status = 1;
      return exit_status;
    }
  lal = 0;
  for (i = 0; i < n; i++)
    {
      fscanf(fpin, "%ld", &row[i]);
      lal += row[i];
    }
  if (!(a = NAG_ALLOC(lal, double)) ||
      !(al = NAG_ALLOC(lal, double)))
    {
      fprintf(fpout, "Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  k2 = 0;
  for (i = 0; i < n; ++i)
    {
      k1 = k2;
      k2 = k2+row[i];
      for (k = k1; k < k2; k++)
        fscanf(fpin, "%lf", &a[k]);
    }
  /* nag_real_cholesky_skyline (f01mcc).
   * LDL^T factorization of real symmetric positive-definite
   * variable-bandwidth (skyline) matrix
   */
  nag_real_cholesky_skyline(n, a, lal, row, al, d, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_real_cholesky_skyline (f01mcc).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }
  fprintf(fpout, "\n");
  fprintf(fpout, "   i    d[i]   Row i of unit lower triangle\n\n");
  k2 = 0;
  for (i = 0; i < n; ++i)
    {
      k1 = k2;
      k2 = k2+row[i];
      fprintf(fpout, " %3ld%8.3f", i, d[i]);
      for (k = k1; k < k2; k++)
        fprintf(fpout, "%8.3f", al[k]);
      fprintf(fpout, "\n");
    }
 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  if (row) NAG_FREE(row);
  if (a) NAG_FREE(a);
  if (al) NAG_FREE(al);
  if (d) NAG_FREE(d);
  return exit_status;
}