/* nag_dstedc (f08jhc) Example Program.
 *
 * Copyright 2011 Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */

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

int main(void)
{
  /* Scalars */
  Integer       i, j, k, kd, n, pdab, pdq;
  Integer       exit_status = 0;
  /* Arrays */
  char          nag_enum_arg[40];
  double        *ab = 0, *d = 0, *e = 0, *q = 0;
  /* Nag Types */
  Nag_OrderType order;
  Nag_UploType  uplo;
  NagError      fail;

#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]
#define Q(I, J) q[(J - 1) * pdq + I - 1]
  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]
#define Q(I, J) q[(I - 1) * pdq + J - 1]
  order = Nag_RowMajor;
#endif
  
  INIT_FAIL(fail);
  
  printf("nag_dstedc (f08jhc) Example Program Results\n\n");
  
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%ld%ld%*[^\n]", &n, &kd);

  /* Read uplo */
  scanf("%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);

  pdab = kd + 1;
  
#ifdef NAG_COLUMN_MAJOR
  pdq = n;
#else
  pdq = n;
#endif
  
  /* Allocate memory */
  if (!(ab = NAG_ALLOC(pdab*n, double)) ||
      !(d = NAG_ALLOC(n, double)) ||
      !(e = NAG_ALLOC(n-1, double)) ||
      !(q = NAG_ALLOC(n*n, double)))
    {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  
  /* Read the upper or lower triangular part of the band matrix A
   * from data file.
   */
  k = kd + 1;
  if (uplo == Nag_Upper) {
    for (i = 1; i <= n; ++i)
      for (j = i; j <= MIN(n, i + kd); ++j)
        scanf("%lf", &AB_UPPER(i, j));
    scanf("%*[^\n]");
  }
  else if (uplo == Nag_Lower) {
    for (i = 1; i <= n; ++i)
      for (j = MAX(1, i - kd); j <= i; ++j)
        scanf("%lf", &AB_LOWER(i, j));
    scanf("%*[^\n]");
  }
  
  /* nag_dsbtrd (f08hec).
   * Reduce A to tridiagonal form T = (Q**T)*A*Q, and form Q.
   */
  nag_dsbtrd(order, Nag_FormQ, uplo, n, kd, ab, pdab, d, e, q, pdq, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dsbtrd (f08hec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  
  /* nag_dstedc (f08jhc)
   * Calculate all the eigenvalues and eigenvectors of A,
   * from T and Q.
   */
  nag_dstedc(order, Nag_OrigEigVecs, n, d, e, q, pdq, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dstedc (f08jhc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

  /* Normalize the eigenvectors */
  for(j=1; j<=n; j++)
    for(i=n; i>=1; i--)
      Q(i, j) = Q(i, j) / Q(1,j);
      
  /* Print eigenvalues and eigenvectors */
  printf("%s\n", "Eigenvalues");  
  for (i = 0; i < n; ++i)
    printf("%8.4f%s", d[i], (i+1)%8 == 0?"\n":" ");
  printf("\n\n");
  
  /* nag_gen_real_mat_print (x04cac).
   * Print eigenvectors.
   */
  fflush(stdout);
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                         n, q, pdq, "Eigenvectors", 0, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n",
             fail.message);
      exit_status = 1;
      goto END;
    }
  
 END:
  if (ab) NAG_FREE(ab);
  if (d) NAG_FREE(d);
  if (e) NAG_FREE(e);
  if (q) NAG_FREE(q);
  
  return exit_status;
}

#undef AB_UPPER
#undef AB_LOWER
#undef Q