/* nag_dsyevr (f08fdc) 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 */
  double        abstol, vl = 0.0, vu = 0.0;
  Integer       exit_status = 0, i, il, iu, j, m, n;
  Integer       pda, pdz;
  /* Arrays */
  double        *a = 0, *w = 0, *z = 0;
  Integer       *isuppz = 0;
  /* Nag Types */
  Nag_OrderType order;
  NagError      fail;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
#define Z(I, J) z[(J - 1) * pdz + I - 1]
  order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
#define Z(I, J) z[(I - 1) * pdz + J - 1]
  order = Nag_RowMajor;
#endif
  
  INIT_FAIL(fail);
  
  printf("nag_dsyevr (f08fdc) Example Program Results\n\n");
  
  /* Skip heading in data file and read n and the lower and upper
   * indices of the smallest and largest eigenvalues to be found
   */
  scanf("%*[^\n]");
  scanf("%ld%ld%ld%*[^\n]", &n, &il, &iu);
  
  m = iu - il + 1;
  /* Allocate memory */
  if (!(a = NAG_ALLOC(n*n, double)) ||
      !(w = NAG_ALLOC(n, double)) ||
      !(z = NAG_ALLOC(n*n, double)) ||
      !(isuppz = NAG_ALLOC(m*2, Integer)))
    {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  
  pda = n;
  pdz = n;
  
  /* Read the upper triangular part of the matrix A from data file */
  for (i = 1; i <= n; ++i)
    for (j = i; j <= n; ++j)
      scanf("%lf", &A(i, j));
  scanf("%*[^\n]");
  
  /* Set the absolute error tolerance for eigenvalues. With abstol
   * set to zero, the default value is used instead.
   */
  abstol = 0.0;
  
  /* nag_dsyevr (f08fdc).
   * Solve the symmetric eigenvalue problem.
   */
  nag_dsyevr(order, Nag_DoBoth, Nag_Indices, Nag_Upper, n, a, pda, vl, vu, il,
             iu, abstol, &m, w, z, pdz, isuppz, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dsyevr (f08fdc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  
  /* Normalize the eigenvectors */
  for(j=1; j<=m; j++)
    for(i=n; i>=1; i--)
      Z(i, j) = Z(i, j) / Z(1,j);
  
  /* Print solution */
  printf("Selected eigenvalues\n");
  for (j = 0; j < m; ++j)
    printf("%8.4f%s", w[j], (j+1)%8 == 0?"\n":" ");
  printf("\n");

  /* nag_gen_real_mat_print (x04cac).
   * Print selected eigenvectors.
   */
  fflush(stdout);
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z,
                         pdz, "Selected 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;
    }
  
 END:
  if (a) NAG_FREE(a);
  if (w) NAG_FREE(w);
  if (z) NAG_FREE(z);
  if (isuppz) NAG_FREE(isuppz);
  
  return exit_status;
}

#undef A
#undef Z