/* nag_real_qr (f01qcc) Example Program.
 *
 * Copyright 1990 Numerical Algorithms Group.
 *
 * Mark 1, 1990.
 * Mark 8 revised, 2004.
 */

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

#define A(I,J) a[(I)*tda + J]
int main(void)
{

  Integer exit_status=0, i, j, m, n, tda;
  NagError fail;
  double *a=0, *zeta=0;

  INIT_FAIL(fail);
  Vprintf("nag_real_qr (f01qcc) Example Program Results\n");
  Vscanf(" %*[^\n]"); /* skip headings in data file */
  Vscanf(" %*[^\n]");

  Vscanf("%ld%ld", &m, &n);
  if (n>=0 && m>=n)
    {
      if ( !( zeta = NAG_ALLOC(n, double)) ||
           !( a = NAG_ALLOC(m*n, double)) )
        {
          Vprintf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
      tda = n;
    }
  else
    {
      Vprintf("Invalid n or m.\n");
      exit_status = 1;
      return exit_status;
    }
  Vscanf(" %*[^\n]"); /* skip next heading */
  for (i = 0; i < m; ++i)   /* Read matrix A */
    for (j = 0; j < n; ++j)
      Vscanf("%lf", &A(i,j));

  /* Find the QR factorization of A */
  /* nag_real_qr (f01qcc).
   * QR factorization of real m by n matrix (m~>=~n)
   */
  nag_real_qr(m, n, a, tda, zeta, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_real_qr (f01qcc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

  Vprintf("QR factorization of A\n\n");
  Vprintf("Vector zeta\n");
  for (i = 0; i < n; ++i)
    Vprintf(" %8.4f", zeta[i]);
  Vprintf("\n\n");
  Vprintf("Matrix A after factorization (upper triangular part is R)\n");
  for (i = 0; i < m; ++i)
    {
      for (j = 0; j < n; ++j)
        Vprintf(" %8.4f", A(i,j));
      Vprintf("\n");
    }
 END:
  if (zeta) NAG_FREE(zeta);
  if (a) NAG_FREE(a);
  return exit_status;
}