/* nag_dsterf (f08jfc) Example Program.
 *
 * Copyright 2001 Numerical Algorithms Group.
 *
 * Mark 7, 2001.
 */

#include <stdio.h>
#include <nag.h>
#include <nagx04.h>
#include <nag_stdlib.h>
#include <nagf08.h>

int main(int argc, char *argv[])
{
  FILE     *fpin, *fpout;
  /* Scalars */
  Integer  i, n, d_len, e_len;
  Integer  exit_status = 0;
  NagError fail;
  /* Arrays */
  double   *d = 0, *e = 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_dsterf (f08jfc) Example Program Results\n\n");

  /* Skip heading in data file */
  fscanf(fpin, "%*[^\n] ");
  fscanf(fpin, "%ld%*[^\n] ", &n);
  d_len = n;
  e_len = n - 1;

  /* Allocate memory */
  if (!(d = NAG_ALLOC(d_len, double)) ||
      !(e = NAG_ALLOC(e_len, double)))
    {
      fprintf(fpout, "Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  /* Read T from data file */
  for (i = 0; i < d_len; ++i)
    fscanf(fpin, "%lf", &d[i]);
  for (i = 0; i < e_len; ++i)
    fscanf(fpin, "%lf", &e[i]);
  /* Calculate all the eigenvalues of T*/
  /* nag_dsterf (f08jfc).
   * All eigenvalues of real symmetric tridiagonal matrix,
   * root-free variant of QL or QR
   */
  nag_dsterf(n, d, e, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dsterf (f08jfc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print eigenvalues */
  fprintf(fpout, " Eigenvalues\n");
  for (i = 0; i < n; ++i)
    fprintf(fpout, "  %7.4lf", d[i]);
  fprintf(fpout, "\n");
 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  if (d) NAG_FREE(d);
  if (e) NAG_FREE(e);
  return exit_status;
}