/* nag_dopmtr (f08ggc) 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(void)
{
  /* Scalars */
  Integer  ap_len, i, j, m, n, nsplit, pdz, d_len, e_len;
  Integer  tau_len;
  Integer  exit_status=0;
  double   vl=0.0, vu=0.0;
  NagError fail;
  Nag_UploType  uplo;
  Nag_OrderType order;
  /* Arrays */
  char    uplo_char[2];
  Integer *iblock=0, *ifailv=0, *isplit=0;
  double  *ap=0, *d=0, *e=0, *tau=0, *w=0, *z=0;

#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]
  order = Nag_ColMajor;
#else
#define A_LOWER(I,J) ap[I*(I-1)/2 + J - 1]
#define A_UPPER(I,J) ap[(2*n-I)*(I-1)/2 + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);
  Vprintf("nag_dopmtr (f08ggc) Example Program Results\n\n");

  /* Skip heading in data file */
  Vscanf("%*[^\n] ");
  Vscanf("%ld%*[^\n] ", &n);
  pdz = n;

  ap_len = n*(n+1)/2;
  tau_len = n-1;
  d_len = n;
  e_len = n-1;
  /* Allocate memory */
  if ( !(ap = NAG_ALLOC(ap_len, double)) ||
       !(d = NAG_ALLOC(d_len, double)) ||
       !(e = NAG_ALLOC(e_len, double)) ||
       !(iblock = NAG_ALLOC(n, Integer)) ||
       !(ifailv = NAG_ALLOC(n, Integer)) ||
       !(isplit = NAG_ALLOC(n, Integer)) ||
       !(w = NAG_ALLOC(n, double)) ||
       !(tau = NAG_ALLOC(tau_len, double)) ||
       !(z = NAG_ALLOC(n * n, double)) )
    {
      Vprintf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  /* Read A from data file */
  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;
    }
  if (uplo == Nag_Upper)
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = i; j <= n; ++j)
            Vscanf("%lf", &A_UPPER(i,j));
        }
      Vscanf("%*[^\n] ");
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = 1; j <= i; ++j)
            Vscanf("%lf", &A_LOWER(i,j));
        }
      Vscanf("%*[^\n] ");
    }

  /* Reduce A to tridiagonal form T = (Q**T)*A*Q */
  /* nag_dsptrd (f08gec).
   * Orthogonal reduction of real symmetric matrix to
   * symmetric tridiagonal form, packed storage
   */
  nag_dsptrd(order, uplo, n, ap, d, e, tau, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dsptrd (f08gec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Calculate the two smallest eigenvalues of T (same as A) */
  /* nag_dstebz (f08jjc).
   * Selected eigenvalues of real symmetric tridiagonal matrix
   * by bisection
   */
  nag_dstebz(Nag_Indices, Nag_ByBlock, n, vl, vu, 1, 2, 0.0,
             d, e, &m, &nsplit, w, iblock, isplit, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dstebz (f08jjc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

  /* Print eigenvalues */
  Vprintf("Eigenvalues\n");
  for (i = 0; i < m; ++i)
    Vprintf("%8.4f%s", w[i], (i+1)%8==0 ?"\n":" ");
  Vprintf("\n\n");
  /* Calculate the eigenvectors of T storing the result in Z */
  /* nag_dstein (f08jkc).
   * Selected eigenvectors of real symmetric tridiagonal
   * matrix by inverse iteration, storing eigenvectors in real
   * array
   */
  nag_dstein(order, n, d, e, m, w, iblock, isplit, z, pdz, ifailv,
             &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dstein (f08jkc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Calculate all the eigenvectors of A = Q*(eigenvectors of T) */
  /* nag_dopmtr (f08ggc).
   * Apply orthogonal transformation determined by nag_dsptrd
   * (f08gec)
   */
  nag_dopmtr(order, Nag_LeftSide, uplo, Nag_NoTrans, n, m, ap,
             tau, z, pdz, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dopmtr (f08ggc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print eigenvectors */
  /* nag_gen_real_mat_print (x04cac).
   * Print real general matrix (easy-to-use)
   */
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z,
                         pdz, "Eigenvectors", 0, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("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 (d) NAG_FREE(d);
  if (e) NAG_FREE(e);
  if (iblock) NAG_FREE(iblock);
  if (ifailv) NAG_FREE(ifailv);
  if (isplit) NAG_FREE(isplit);
  if (tau) NAG_FREE(tau);
  if (w) NAG_FREE(w);
  if (z) NAG_FREE(z);

  return exit_status;
}