/* nag_real_band_lin_solve (f04bbc) Example Program.
 *
 * Copyright 2004 Numerical Algorithms Group.
 *
 * Mark 8, 2004.
 */

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf04.h>
#include <nagx04.h>

int main(void)
{

  /* Scalars */
  double errbnd, rcond;
  Integer exit_status, i, j, kl, ku, n, nrhs, pdab, pdb;

  /* Arrays */
  double *ab=0, *b=0;
  Integer *ipiv=0;

  /* Nag Types */
  NagError fail;
  Nag_OrderType order;

#ifdef NAG_COLUMN_MAJOR
#define AB(I,J) ab[(J-1)*pdab + kl + ku + I - J]
#define B(I,J)   b[(J-1)*pdb +  I - 1]
  order = Nag_ColMajor;
#else
#define AB(I,J) ab[(I-1)*pdab + kl + J - I]
#define B(I,J)   b[(I-1)*pdb +  J - 1]
  order = Nag_RowMajor;
#endif

  exit_status = 0;
  INIT_FAIL(fail);
  Vprintf("nag_real_band_lin_solve (f04bbc) Example Program Results\n\n");

  /* Skip heading in data file */
  Vscanf("%*[^\n] ");

  Vscanf("%ld%ld%ld%ld%*[^\n] ",
         &n,  &kl,  &ku,  &nrhs);
  if (n >= 0 && kl >=0 && ku >=0 && nrhs >=0)
    {
      /* Allocate memory */
      if ( !(ab = NAG_ALLOC((2*kl+ku+1)*n, double)) ||
           !(b = NAG_ALLOC(n*nrhs, double)) ||
           !(ipiv = NAG_ALLOC(n, Integer)) )
        {
          Vprintf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
      pdab = 2*kl+ku+1;
#ifdef NAG_COLUMN_MAJOR
      pdb = n;
#else
      pdb = nrhs;
#endif
    }
  else
    {
      Vprintf("%s\n",   "One or more of nmax, kl, ku or nrhs is"
              " too small");
      exit_status = 1;
      return exit_status;
    }
  /* Read A and B from data file */
  for (i = 1; i <= n; ++i)
    {
      for (j = MAX(i - kl,1); j <= MIN(i + ku,n); ++j)
        {
          Vscanf("%lf", &AB(i,j));
        }
    }
  Vscanf("%*[^\n] ");

  for (i = 1; i <= n; ++i)
    {
      for (j = 1; j <= nrhs; ++j)
        {
          Vscanf("%lf", &B(i,j));
        }
    }
  Vscanf("%*[^\n] ");

  /* Solve the equations AX = B for X */
  /* nag_real_band_lin_solve (f04bbc).
   * Computes the solution and error-bound to a real banded
   * system of linear equations
   */
  nag_real_band_lin_solve(order, n, kl, ku, nrhs, ab, pdab, ipiv, b,
                          pdb, &rcond, &errbnd, &fail);
  if (fail.code == NE_NOERROR)
    {

      /* Print solution, estimate of condition number and approximate */
      /* error bound */

      /* nag_gen_real_mat_print (x04cac).
       * Print real general matrix (easy-to-use)
       */
      nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag,
                             n, nrhs, b, pdb, "Solution", 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%s\n%6s%9.1e\n\n\n",
              "Estimate of condition number",  "",  1.0/rcond);

      Vprintf("%s\n%6s%9.1e\n\n",
              "Estimate of error bound for computed solutions",  "",
              errbnd);
    }
  else if (fail.code == NE_RCOND)
    {

      /* Matrix A is numerically singular.  Print estimate of */
      /* reciprocal of condition number and solution */
      Vprintf("\n");
      Vprintf("%s\n%6s%9.1e\n\n\n",
              "Estimate of reciprocal of condition number",  "",  rcond);
      /* nag_gen_real_mat_print (x04cac), see above. */
      nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag,
                             n, nrhs, b, pdb, "Solution", 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;
        }

    }
  else if (fail.code == NE_SINGULAR)
    {

      /* The upper triangular matrix U is exactly singular.  Print */
      /* details of factorization */
      Vprintf("\n");
      /* nag_band_real_mat_print (x04cec).
       * Print real packed banded matrix (easy-to-use)
       */
      nag_band_real_mat_print(order, n, n, kl, kl+ku, ab, pdab,
                              "Details of factorization", 0, &fail);
      if (fail.code != NE_NOERROR)
        {
          Vprintf("Error from nag_band_real_mat_print (x04cec).\n%s\n",
                  fail.message);
          exit_status = 1;
          goto END;
        }

      /* Print pivot indices */
      Vprintf("\n%s\n",   "Pivot indices");
      for (i = 1; i <= n; ++i)
        {
          Vprintf("%11ld%s", ipiv[i - 1],
                  i%7 == 0 || i == n ?"\n":" ");
        }
      Vprintf("\n");
    }
 END:
  if (ab) NAG_FREE(ab);
  if (b) NAG_FREE(b);
  if (ipiv) NAG_FREE(ipiv);

  return exit_status;
}