/* nag_dbdsqr (f08mec) 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, n, pdvt, pdu, d_len, e_len;
  Integer  exit_status=0;
  NagError fail;
  Nag_UploType  uplo;
  Nag_OrderType order;
  /* Arrays */
  char   uplo_char[2];
  double *c=0, *d=0, *e=0, *u=0, *vt=0;

  INIT_FAIL(fail);
  Vprintf("nag_dbdsqr (f08mec) Example Program Results\n\n");

  /* Skip heading in data file */
  Vscanf("%*[^\n] ");
  Vscanf("%ld%*[^\n] ", &n);
#ifdef NAG_COLUMN_MAJOR
#define U(I,J) u[(J-1)*pdu + I - 1]
#define VT(I,J) vt[(J-1)*pdvt + I - 1]
  order = Nag_ColMajor;
  pdu = n;
  pdvt = n;
#else
#define U(I,J) u[(I-1)*pdu + J - 1]
#define VT(I,J) vt[(I-1)*pdvt + J - 1]
  order = Nag_RowMajor;
  pdu = n;
  pdvt = n;
#endif
  d_len = n;
  e_len = n-1;

  /* Allocate memory */
  if ( !(c = NAG_ALLOC(1 * 1, double)) ||
       !(d = NAG_ALLOC(d_len, double)) ||
       !(e = NAG_ALLOC(e_len, double)) ||
       !(u = NAG_ALLOC(n * n, double)) ||
       !(vt = NAG_ALLOC(n * n, double)) )
    {
      Vprintf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  /* Read B from data file */
  for (i = 1; i <= n; ++i)
    Vscanf("%lf", &d[i-1]);
  Vscanf("%*[^\n] ");
  for (i = 1; i <= n-1; ++i)
    Vscanf("%lf", &e[i-1]);
  Vscanf("%*[^\n] ");
  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;
    }

  /* Initialise U and VT to be the unit matrix */
  for (i = 1; i <= n; ++i)
    {
      for (j = 1; j <= n; ++j)
        {
          U(i,j) = 0.0;
          VT(i,j) = 0.0;
        }
      U(i,i) = 1.0;
      VT(i,i) = 1.0;
    }

  /* Calculate the SVD of B */
  /* nag_dbdsqr (f08mec).
   * SVD of real bidiagonal matrix reduced from real general
   * matrix
   */
  nag_dbdsqr(order, uplo, n, n, n, 0, d, e, vt, pdvt, u, pdu, c,
             1, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dbdsqr (f08mec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print singular values, left & right singular vectors */
  Vprintf("\nSingular values\n");
  for (i = 1; i <= n; ++i)
    Vprintf("%8.4f%s", d[i-1], i%8==0 ?"\n":" ");
  Vprintf("\n\n");

  /* nag_gen_real_mat_print (x04cac).
   * Print real general matrix (easy-to-use)
   */
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n,
                         vt, pdvt, "Right singular vectors, by row", 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;
    }
  Vprintf("\n");
  /* nag_gen_real_mat_print (x04cac), see above. */
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n,
                         u, pdu, "Left singular vectors, by column", 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 (c) NAG_FREE(c);
  if (d) NAG_FREE(d);
  if (e) NAG_FREE(e);
  if (u) NAG_FREE(u);
  if (vt) NAG_FREE(vt);

  return exit_status;
}