/* nag_dsbtrd (f08hec) Example Program.
 *
 * Copyright 2001 Numerical Algorithms Group.
 *
 * Mark 7, 2001.
 */

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

int main(int argc, char *argv[])
{
  FILE          *fpin, *fpout;
  char          *outfile = 0;
  /* Scalars */
  Integer       i, j, k, kd, n, pdab, pdz, d_len, e_len;
  Integer       exit_status = 0;
  NagError      fail;
  Nag_UploType  uplo;
  Nag_OrderType order;
  /* Arrays */
  char          nag_enum_arg[40];
  double        *ab = 0, *d = 0, *e = 0, *z = 0;

#ifdef NAG_COLUMN_MAJOR
#define AB_UPPER(I, J) ab[(J - 1) * pdab + k + I - J - 1]
#define AB_LOWER(I, J) ab[(J - 1) * pdab + I - J]
  order = Nag_ColMajor;
#else
#define AB_UPPER(I, J) ab[(I - 1) * pdab + J - I]
#define AB_LOWER(I, J) ab[(I - 1) * pdab + k + J - I - 1]
  order = Nag_RowMajor;
#endif

  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);
  (void) nag_example_file_io(argc, argv, "-nag_write", &outfile);
  fprintf(fpout, "nag_dsbtrd (f08hec) Example Program Results\n\n");

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

  /* Allocate memory */
  if (!(ab = NAG_ALLOC(pdab * n, double)) ||
      !(d = NAG_ALLOC(d_len, double)) ||
      !(e = NAG_ALLOC(e_len, double)) ||
      !(z = NAG_ALLOC(pdz * n, double)))
    {
      fprintf(fpout, "Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  /* Read A from data file */
  fscanf(fpin, "%s%*[^\n] ", nag_enum_arg);
  /* nag_enum_name_to_value(x04nac).
   * Converts NAG enum member name to value
   */
  uplo = (Nag_UploType) nag_enum_name_to_value(nag_enum_arg);
  k = kd + 1;
  if (uplo == Nag_Upper)
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = i; j <= MIN(i + kd, n); ++j)
            fscanf(fpin, "%lf", &AB_UPPER(i, j));
        }
      fscanf(fpin, "%*[^\n] ");
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = MAX(1, i - kd); j <= i; ++j)
            fscanf(fpin, "%lf", &AB_LOWER(i, j));
        }
      fscanf(fpin, "%*[^\n] ");
    }

  /* Reduce A to tridiagonal form */
  /* nag_dsbtrd (f08hec).
   * Orthogonal reduction of real symmetric band matrix to
   * symmetric tridiagonal form
   */
  nag_dsbtrd(order, Nag_FormQ, uplo, n, kd, ab, pdab, d, e,
             z, pdz, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dsbtrd (f08hec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Calculate all the eigenvalues and eigenvectors of A */
  /* nag_dsteqr (f08jec).
   * All eigenvalues and eigenvectors of real symmetric
   * tridiagonal matrix, reduced from real symmetric matrix
   * using implicit QL or QR
   */
  nag_dsteqr(order, Nag_UpdateZ, n, d, e, z, pdz, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dsteqr (f08jec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print eigenvalues and eigenvectors */
  fprintf(fpout, "Eigenvalues\n");
  for (i = 1; i <= n; ++i)
    fprintf(fpout, "%8.4f%s", d[i-1], i%8 == 0?"\n":" ");
  fprintf(fpout, "\n\n");
  /* nag_gen_real_mat_print (x04cac).
   * Print real general matrix (easy-to-use)
   */
  if (outfile) fclose(fpout);
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n,
                         z, pdz, "Eigenvectors", outfile, &fail);
  if (outfile && !(fpout = fopen(outfile, "a")))
    {
      exit_status = 2;
      goto END;
    }
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_gen_real_mat_print (x04cac).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }
 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  if (ab) NAG_FREE(ab);
  if (d) NAG_FREE(d);
  if (e) NAG_FREE(e);
  if (z) NAG_FREE(z);

  return exit_status;
}