/* nag_dspgvx (f08tbc) Example Program.
 *
 * Copyright 2011 Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */

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

int main(void)
{
  /* Scalars */
  double        abstol, vl, vu;
  Integer       i, il = 0, iu = 0, j, m, n, pdz;
  Integer       exit_status = 0;
  /* Arrays */
  double        *ap = 0, *bp = 0, *w = 0, *z = 0;
  Integer       *index = 0;
  char          nag_enum_arg[40];

  /* Nag Types */
  NagError      fail;
  Nag_OrderType order;
  Nag_UploType  uplo;

#ifdef NAG_COLUMN_MAJOR
#define A_UPPER(I, J) ap[J*(J-1)/2 + I - 1]
#define A_LOWER(I, J) ap[(2*n-J)*(J-1)/2 + I - 1]
#define B_UPPER(I, J) bp[J*(J-1)/2 + I - 1]
#define B_LOWER(I, J) bp[(2*n-J)*(J-1)/2 + I - 1]
#define Z(I, J) z[(J-1)*pdz + I - 1]
  order = Nag_ColMajor;
#else
#define A_UPPER(I, J) ap[(2*n-I)*(I-1)/2 + J - 1]
#define A_LOWER(I, J) ap[I*(I-1)/2 + J - 1]
#define B_UPPER(I, J) bp[(2*n-I)*(I-1)/2 + J - 1]
#define B_LOWER(I, J) bp[I*(I-1)/2 + J - 1]
#define Z(I, J) z[(I-1)*pdz + J - 1]
  order = Nag_RowMajor;
#endif
  
  INIT_FAIL(fail);
  
  
  printf("nag_dspgvx (f08tbc) Example Program Results\n\n");
  
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%ld%*[^\n]", &n);
  if (n < 0)
    {
      printf("Invalid n\n");
      exit_status = 1;
      goto END;;
    }
  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);

  m = n;
  pdz = n;
  /* Allocate memory */
  if (!(ap    = NAG_ALLOC(n*(n+1)/2, double)) ||
      !(bp    = NAG_ALLOC(n*(n+1)/2, double)) ||
      !(w     = NAG_ALLOC(n, double)) ||
      !(z     = NAG_ALLOC(n * m, double)) ||
      !(index = NAG_ALLOC(n, Integer)))
    {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  
  /* Read the lower and upper bounds of the interval to be searched. */
  scanf("%lf%lf%*[^\n]", &vl, &vu);
  /* Read the triangular parts of the matrices A and B from data file. */
  if (uplo == Nag_Upper)
    {
      for (i = 1; i <= n; ++i)
	for (j = i; j <= n; ++j) scanf("%lf", &A_UPPER(i, j));
      scanf("%*[^\n]");
      for (i = 1; i <= n; ++i)
	for (j = i; j <= n; ++j) scanf("%lf", &B_UPPER(i, j));
    }
  else if (uplo == Nag_Lower)
    {
      for (i = 1; i <= n; ++i)
	for (j = 1; j <= i; ++j) scanf("%lf", &A_LOWER(i, j));
      scanf("%*[^\n]");
      for (i = 1; i <= n; ++i)
	for (j = 1; j <= i; ++j) scanf("%lf", &B_LOWER(i, j));
    }
  scanf("%*[^\n]");
   
  /* use the default absolute error tolerance for eigenvalues. */
  abstol = 0.0;
  
  /* Solve the generalized symmetric eigenvalue problem A*x = lambda*B*x
   * using nag_dspgvx (f08tbc).
   */
  nag_dspgvx(order, 1, Nag_DoBoth, Nag_Interval, uplo, n, ap, bp, vl, vu, il,
             iu, abstol, &m, w, z, pdz, index, &fail);
  
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dspgvx (f08tbc).\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 eigensolution */
  printf("Number of eigenvalues found =%5ld\n\n", m);
  printf(" Eigenvalues\n   ");
  for (j = 0; j < m; ++j) printf(" %8.4f%s", w[j], j%8 == 7?"\n":"");
  printf("\n");
      
  /* Print normalized vectors using nag_gen_real_mat_print (x04cac). */
  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;
      goto END;
    }
  
 END:
  if (ap) NAG_FREE(ap);
  if (bp) NAG_FREE(bp);
  if (w) NAG_FREE(w);
  if (z) NAG_FREE(z);
  if (index) NAG_FREE(index);
  
  return exit_status;
}