/* nag_dgbrfs (f07bhc) Example Program.
 *
 * Copyright 2001 Numerical Algorithms Group.
 *
 * Mark 7, 2001.
 */

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

int main(int argc, char *argv[])
{
  FILE          *fpin, *fpout;
  char          *outfile = 0;
  /* Scalars */
  Integer       i, ipiv_len, j, kl, ku, n, nrhs, pdab, pdafb, pdb, pdx;
  Integer       exit_status = 0;
  NagError      fail;
  Nag_OrderType order;

  /* Arrays */
  double        *ab = 0, *afb = 0, *b = 0, *berr = 0, *ferr = 0, *x = 0;
  Integer       *ipiv = 0;

#ifdef NAG_COLUMN_MAJOR
#define AB(I, J)  ab[(J-1)*pdab +  ku + I - J]
#define AFB(I, J) afb[(J-1)*pdafb + kl + ku + I - J]
#define B(I, J)   b[(J-1)*pdb + I - 1]
#define X(I, J)   x[(J-1)*pdx + I - 1]
  order = Nag_ColMajor;
#else
#define AB(I, J)  ab[(I-1)*pdab + kl + J - I]
#define AFB(I, J) afb[(I-1)*pdafb + kl + J - I]
#define B(I, J)   b[(I-1)*pdb + J - 1]
#define X(I, J)   x[(I-1)*pdx + 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_dgbrfs (f07bhc) Example Program Results\n\n");

  /* Skip heading in data file */
  fscanf(fpin, "%*[^\n] ");
  fscanf(fpin, "%ld%ld%ld%ld%*[^\n] ", &n, &nrhs,
         &kl, &ku);
  ipiv_len = n;
  pdab = kl + ku + 1;
  pdafb = 2*kl + ku + 1;
#ifdef NAG_COLUMN_MAJOR
  pdb = n;
  pdx = n;
#else
  pdb = nrhs;
  pdx = nrhs;
#endif

  /* Allocate memory */
  if (!(ab = NAG_ALLOC((kl+ku+1) * n, double)) ||
      !(afb = NAG_ALLOC((2*kl+ku+1) * n, double)) ||
      !(b = NAG_ALLOC(nrhs * n, double)) ||
      !(x = NAG_ALLOC(nrhs * n, double)) ||
      !(berr = NAG_ALLOC(nrhs, double)) ||
      !(ferr = NAG_ALLOC(nrhs, double)) ||
      !(ipiv = NAG_ALLOC(ipiv_len, Integer)))
    {
      fprintf(fpout, "Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  /* Set A to zero to avoid referencing unitialized elements */
  for (i = 0; i < n*(kl+ku+1); ++i)
    ab[i] = 0.0;
  /* Read A from data file */
  for (i = 1; i <= n; ++i)
    {
      for (j = MAX(i-kl, 1); j <= MIN(i+ku, n); ++j)
        fscanf(fpin, "%lf", &AB(i, j));
    }
  fscanf(fpin, "%*[^\n] ");
  /* Read B from data file */
  for (i = 1; i <= n; ++i)
    {
      for (j = 1; j <= nrhs; ++j)
        fscanf(fpin, "%lf", &B(i, j));
    }
  fscanf(fpin, "%*[^\n] ");
  /* Copy A to AFB and B to X */
  for (i = 1; i <= n; ++i)
    {
      for (j = MAX(i-kl, 1); j <= MIN(i+ku, n); ++j)
        AFB(i, j) = AB(i, j);
    }
  for (i = 1; i <= n; ++i)
    {
      for (j = 1; j <= nrhs; ++j)
        X(i, j) = B(i, j);
    }
  /* Factorize A in the array AFB */
  /* nag_dgbtrf (f07bdc).
   * LU factorization of real m by n band matrix
   */
  nag_dgbtrf(order, n, n, kl, ku, afb, pdafb, ipiv, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dgbtrf (f07bdc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Compute solution in the array X */
  /* nag_dgbtrs (f07bec).
   * Solution of real band system of linear equations,
   * multiple right-hand sides, matrix already factorized by
   * nag_dgbtrf (f07bdc)
   */
  nag_dgbtrs(order, Nag_NoTrans, n, kl, ku, nrhs, afb, pdafb, ipiv,
             x, pdx, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dgbtrs (f07bec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Improve solution, and compute backward errors and  */
  /* estimated bounds on the forward errors */
  /* nag_dgbrfs (f07bhc).
   * Refined solution with error bounds of real band system of
   * linear equations, multiple right-hand sides
   */
  nag_dgbrfs(order, Nag_NoTrans, n, kl, ku, nrhs, ab, pdab, afb, pdafb,
             ipiv, b, pdb, x, pdx, ferr, berr, &fail);
  if (fail.code != NE_NOERROR)
    {
      fprintf(fpout, "Error from nag_dgbrfs (f07bhc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print solution */
  /* 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, x,
                         pdx, "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;
    }
  /* Print forward and backward errors */
  fprintf(fpout, "\nBackward errors (machine-dependent)\n");

  for (j = 1; j <= nrhs; ++j)
    fprintf(fpout, "%11.1e%s", berr[j-1], j%7 == 0?"\n":" ");

  fprintf(fpout, "\nEstimated forward error bounds (machine-dependent)\n");

  for (j = 1; j <= nrhs; ++j)
    fprintf(fpout, "%11.1e%s", ferr[j-1], j%7 == 0?"\n":" ");
  fprintf(fpout, "\n");
 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  if (ab) NAG_FREE(ab);
  if (afb) NAG_FREE(afb);
  if (b) NAG_FREE(b);
  if (x) NAG_FREE(x);
  if (berr) NAG_FREE(berr);
  if (ferr) NAG_FREE(ferr);
  if (ipiv) NAG_FREE(ipiv);
  return exit_status;
}