/* nag_dsbgst (f08uec) Example Program.
 *
 * Copyright 2001 Numerical Algorithms Group.
 *
 * Mark 7, 2001.
 */

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

int main(void)
{
  /* Scalars */
  Integer  i, j, k1, k2, ka, kb, n, pdab, pdbb, pdx, d_len, e_len;
  Integer  exit_status=0;
  NagError fail;
  Nag_UploType   uplo;
  Nag_OrderType  order;
  /* Arrays */
  char   uplo_char[2];
  double *ab=0, *bb=0, *d=0, *e=0, *x=0;

#ifdef NAG_COLUMN_MAJOR
#define AB_UPPER(I,J) ab[(J-1)*pdab + k1 + I - J - 1]
#define AB_LOWER(I,J) ab[(J-1)*pdab + I - J]
#define BB_UPPER(I,J) bb[(J-1)*pdbb + k2 + I - J - 1]
#define BB_LOWER(I,J) bb[(J-1)*pdbb + 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 + k1 + J - I - 1]
#define BB_UPPER(I,J) bb[(I-1)*pdbb + J - I]
#define BB_LOWER(I,J) bb[(I-1)*pdbb + k2 + J - I - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);
  Vprintf("nag_dsbgst (f08uec) Example Program Results\n\n");

  /* Skip heading in data file */
  Vscanf("%*[^\n] ");
  Vscanf("%ld%ld%ld%*[^\n] ", &n, &ka, &kb);
  pdab = ka + 1;
  pdbb = kb + 1;
  pdx = n;
  d_len = n;
  e_len = n-1;

  /* Allocate memory */
  if ( !(ab = NAG_ALLOC(pdab * n, double)) ||
       !(bb = NAG_ALLOC(pdbb * n, double)) ||
       !(d = NAG_ALLOC(d_len, double)) ||
       !(e = NAG_ALLOC(e_len, double)) ||
       !(x = NAG_ALLOC(n * n, double)) )
    {
      Vprintf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  /* Read whether Upper or Lower part of A is stored */
  Vscanf(" ' %1s '%*[^\n] ", uplo_char);
  if (*(unsigned char *)uplo_char == 'L')
    uplo = Nag_Lower;
  else if (*(unsigned char *)uplo_char == 'U')
    uplo = Nag_Upper;
  else
    {
      Vprintf("Unrecognised character for Nag_UploType type\n");
      exit_status = -1;
      goto END;
    }
  /* Read A and B from data file */
  k1 = ka + 1;
  k2 = kb + 1;
  if (uplo == Nag_Upper)
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = i; j <= MIN(i+ka,n); ++j)
            Vscanf("%lf", &AB_UPPER(i,j));
        }
      Vscanf("%*[^\n] ");
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = MAX(1,i-ka); j <= i; ++j)
            Vscanf("%lf", &AB_LOWER(i,j));
        }
      Vscanf("%*[^\n] ");
    }
  if (uplo == Nag_Upper)
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = i; j <= MIN(i+kb,n); ++j)
            Vscanf("%lf", &BB_UPPER(i,j));
        }
      Vscanf("%*[^\n] ");
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = MAX(1,i-kb); j <= i; ++j)
            Vscanf("%lf", &BB_LOWER(i,j));
        }
      Vscanf("%*[^\n] ");
    }
  /* Compute the split Cholesky factorization of B */
  /* nag_dpbstf (f08ufc).
   * Computes a split Cholesky factorization of real symmetric
   * positive-definite band matrix A
   */
  nag_dpbstf(order, uplo, n, kb, bb, pdbb, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dpbstf (f08ufc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Reduce the problem to standard form C*y = lambda*y, */
  /* storing the result in A */
  /* nag_dsbgst (f08uec).
   * Reduction of real symmetric-definite banded generalized
   * eigenproblem Ax~=~lambda~Bx to standard form
   * Cy~=~lambda~y, such that C has the same bandwidth as A
   */
  nag_dsbgst(order, Nag_DoNotForm, uplo, n, ka, kb, ab, pdab, bb, pdbb,
             x, pdx, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dsbgst (f08uec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Reduce C to tridiagonal form T = (Q**T)*C*Q */
  /* nag_dsbtrd (f08hec).
   * Orthogonal reduction of real symmetric band matrix to
   * symmetric tridiagonal form
   */
  nag_dsbtrd(order, Nag_DoNotForm, uplo, n, ka, ab, pdab, d, e,
             x, pdx, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dsbtrd (f08hec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Calculate the eigenvalues of T (same as C) */
  /* 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)
    {
      Vprintf("Error from nag_dsterf (f08jfc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print eigenvalues */
  Vprintf(" Eigenvalues\n");
  for (i = 0; i < n; ++i)
    Vprintf(" %8.4lf",d[i]);
  Vprintf("\n");
 END:
  if (ab) NAG_FREE(ab);
  if (bb) NAG_FREE(bb);
  if (d) NAG_FREE(d);
  if (e) NAG_FREE(e);
  if (x) NAG_FREE(x);
  return exit_status;
}