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

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

#define A(I, J) a[(I) *tda + J]
int main(int argc, char *argv[])
{
  FILE     *fpin, *fpout;

  Integer  exit_status = 0, i, j, m, n, tda;
  NagError fail;
  double   *a = 0, *zeta = 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_qr (f01qcc) Example Program Results\n");
  fscanf(fpin, " %*[^\n]"); /* skip headings in data file */
  fscanf(fpin, " %*[^\n]");

  fscanf(fpin, "%ld%ld", &m, &n);
  if (n >= 0 && m >= n)
    {
      if (!(zeta = NAG_ALLOC(n, double)) ||
          !(a = NAG_ALLOC(m*n, double)))
        {
          fprintf(fpout, "Allocation failure\n");
          exit_status = -1;
          goto END;
        }
      tda = n;
    }
  else
    {
      fprintf(fpout, "Invalid n or m.\n");
      exit_status = 1;
      return exit_status;
    }
  fscanf(fpin, " %*[^\n]"); /* skip next heading */
  for (i = 0; i < m; ++i)   /* Read matrix A */
    for (j = 0; j < n; ++j)
      fscanf(fpin, "%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)
    {
      fprintf(fpout, "Error from nag_real_qr (f01qcc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

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