/* nag_dormtr (f08fgc) 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  i, j, m, n, nsplit, pda, pdz, d_len, e_len, 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  *a=0, *d=0, *e=0, *tau=0, *w=0, *z=0;

#ifdef NAG_COLUMN_MAJOR
#define A(I,J) a[(J-1)*pda + I - 1]
  order = Nag_ColMajor;
#else
#define A(I,J) a[(I-1)*pda + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);
  Vprintf("f08fgc Example Program Results\n\n");

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

  tau_len = n-1;
  d_len = n;
  e_len = n-1;
  /* Allocate memory */
  if ( !(a = NAG_ALLOC(n * n, 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(i,j));
        }
      Vscanf("%*[^\n] ");
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = 1; j <= i; ++j)
            Vscanf("%lf", &A(i,j));
        }
      Vscanf("%*[^\n] ");
    }

  /* Reduce A to tridiagonal form T = (Q**T)*A*Q */
  f08fec(order, uplo, n, a, pda, d, e, tau, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from f08fec.\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Calculate the two smallest eigenvalues of T (same as A) */
  f08jjc(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 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 */
  f08jkc(order, n, d, e, m, w, iblock, isplit, z, pdz, ifailv,
         &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from f08jkc.\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Calculate all the eigenvectors of A = Q*(eigenvectors of T) */
  f08fgc(order, Nag_LeftSide, uplo, Nag_NoTrans, n, m, a, pda,
         tau, z, pdz, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from f08fgc.\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print eigenvectors */
  x04cac(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z, pdz,
         "Eigenvectors", 0, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from x04cac.\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
 END:
  if (a) NAG_FREE(a);
  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;
}