/* nag_dgelqf (f08ahc) Example Program.
 *
 * Copyright 2001 Numerical Algorithms Group.
 *
 * Mark 7, 2001.
 */

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf07.h>
#include <nagf08.h>
#include <nagx04.h>

int main(int argc, char *argv[])
{
  FILE          *fpin, *fpout;
  char          *outfile = 0;
  /* Scalars */
  Integer       i, j, m, n, nrhs, pda, pdb, tau_len;
  Integer       exit_status = 0;
  NagError      fail;
  Nag_OrderType order;
  /* Arrays */
  double        *a = 0, *b = 0, *tau = 0;

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

  INIT_FAIL(fail);

  /* Check for command-line IO options */
  fpin = nag_example_file_io(argc, argv, "-data", NULL);
  fpout = nag_example_file_io(argc, argv, "-results", NULL);
  (void) nag_example_file_io(argc, argv, "-nag_write", &outfile);
  fprintf(fpout, "nag_dgelqf (f08ahc) Example Program Results\n\n");

  /* Skip heading in data file */
  fscanf(fpin, "%*[^\n] ");
  fscanf(fpin, "%ld%ld%ld%*[^\n] ", &m, &n, &nrhs);

#ifdef NAG_COLUMN_MAJOR
  pda = m;
  pdb = n;
#else
  pda = n;
  pdb = nrhs;
#endif

  tau_len = MIN(m, n);

  /* Allocate memory */
  if (!(a = NAG_ALLOC(m * n, double)) ||
      !(b = NAG_ALLOC(n * nrhs, double)) ||
      !(tau = NAG_ALLOC(tau_len, double)))
    {
      fprintf(fpout, "Allocation failure\n");
      exit_status = -1;
      goto END;
    }

  /* Read A and B from data file */
  for (i = 1; i <= m; ++i)
    {
      for (j = 1; j <= n; ++j)
        fscanf(fpin, "%lf", &A(i, j));
    }
  fscanf(fpin, "%*[^\n] ");
  for (i = 1; i <= m; ++i)
    {
      for (j = 1; j <= nrhs; ++j)
        fscanf(fpin, "%lf", &B(i, j));
    }
  fscanf(fpin, "%*[^\n] ");

  /* Compute the LQ factorization of A */
  /* nag_dgelqf (f08ahc).
   * LQ factorization of real general rectangular matrix
   */
  nag_dgelqf(order, m, n, a, pda, tau, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dgelqf (f08ahc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Solve L*Y = B, storing the result in B */
  /* nag_dtrtrs (f07tec).
   * Solution of real triangular system of linear equations,
   * multiple right-hand sides
   */
  nag_dtrtrs(order, Nag_Lower, Nag_NoTrans, Nag_NonUnitDiag, m,
             nrhs, a, pda, b, pdb, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dtrtrs (f07tec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Set rows (M+1) to N of B to zero */
  if (m < n)
    {
      for (i = m + 1; i <= n; ++i)
        {
          for (j = 1; j <= nrhs; ++j)
            B(i, j) = 0.0;
        }
    }

  /* Compute minimum-norm solution X = (Q**T)*B in B */
  /* nag_dormlq (f08akc).
   * Apply orthogonal transformation determined by nag_dgelqf (f08ahc)
   */
  nag_dormlq(order, Nag_LeftSide, Nag_Trans, n, nrhs, m, a, pda,
             tau, b, pdb, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dormlq (f08akc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

  /* Print minimum-norm solution(s) */
  /* nag_gen_real_mat_print (x04cac).
   * Print real general matrix (easy-to-use)
   */
  if (outfile) fclose(fpout);
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, b,
                         pdb, "Minimum-norm solution(s)", outfile, &fail);
  if (outfile && !(fpout = fopen(outfile, "a")))
    {
      exit_status = 2;
      goto END;
    }
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_gen_real_mat_print (x04cac).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }
 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  if (a) NAG_FREE(a);
  if (b) NAG_FREE(b);
  if (tau) NAG_FREE(tau);
  return exit_status;
}