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

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

int main(void)
{
  Integer exit_status=0, i, k, k1, k2, lal, n, *row=0;
  NagError fail;
  double *a=0, *al=0, *d=0;

  INIT_FAIL(fail);
  Vprintf("nag_real_cholesky_skyline (f01mcc) Example Program Results\n");
  /* Skip heading in data file */
  Vscanf("%*[^\n]");
  Vscanf("%ld", &n);
  if (n>=1)
    {
      if ( !( row = NAG_ALLOC(n, Integer)) ||
           !( d = NAG_ALLOC(n, double)) )
        {
          Vprintf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      Vprintf("Invalid n.\n");
      exit_status = 1;
      return exit_status;
    }
  lal=0;
  for (i=0; i<n; i++)
    {
      Vscanf("%ld", &row[i]);
      lal += row[i];
    }
  if ( !( a = NAG_ALLOC(lal, double)) ||
       !( al = NAG_ALLOC(lal, double)) )
    {
      Vprintf("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++)
        Vscanf("%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)
    {
      Vprintf("Error from nag_real_cholesky_skyline (f01mcc).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }
  Vprintf("\n");
  Vprintf("   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];
      Vprintf(" %3ld%8.3f", i, d[i]);
      for (k=k1; k<k2; k++)
        Vprintf("%8.3f", al[k]);
      Vprintf("\n");
    }
 END:
  if (row) NAG_FREE(row);
  if (a) NAG_FREE(a);
  if (al) NAG_FREE(al);
  if (d) NAG_FREE(d);
  return exit_status;
}