/* nag_real_sym_posdef_band_lin_solve (f04bfc) 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, kd, n, nrhs, pdab, pdb;

  /* Arrays */
  char   nag_enum_arg[20];
  double *ab=0, *b=0;

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

#ifdef NAG_COLUMN_MAJOR
#define AB_U(I,J) ab[(J-1)*pdab + kd + I - J]
#define AB_L(I,J) ab[(J-1)*pdab + I - J]
#define B(I,J)   b[(J-1)*pdb +  I - 1]
  order = Nag_ColMajor;
#else
#define AB_U(I,J) ab[(I-1)*pdab + J - I]
#define AB_L(I,J) ab[(I-1)*pdab + kd + 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_sym_posdef_band_lin_solve (f04bfc)"
          " Example Program Results\n\n");

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

  Vscanf("%ld%ld%ld%*[^\n] ", &n, &kd, &nrhs);
  if (n>0 && kd >0 && nrhs >0)
    {
      /* Allocate memory */
      if ( !(ab = NAG_ALLOC((kd+1)*n, double)) ||
           !(b = NAG_ALLOC(n*nrhs, double)) )
        {
          Vprintf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
      pdab = kd+1;
#ifdef NAG_COLUMN_MAJOR
      pdb = n;
#else
      pdb = nrhs;
#endif
    }
  else
    {
      Vprintf("%s\n", "One or more of n, kd and nrhs is too small");
      exit_status = 1;
      return exit_status;

    }

  /* Read uplo storage name for the matrix A and convert to value. */
  Vscanf("%s%*[^\n] ", nag_enum_arg);

  /* nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);

  if (uplo == Nag_Upper)
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = i; j <= MIN(n,i + kd); ++j)
            {
              Vscanf("%lf", &AB_U(i,j));
            }
          Vscanf("%*[^\n] ");
        }
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = MAX(1,i - kd); j <= i; ++j)
            {
              Vscanf("%lf", &AB_L(i,j));
            }
          Vscanf("%*[^\n] ");
        }
    }

  /* Read B from data file */
  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_sym_posdef_band_lin_solve (f04bfc).
   * Computes the solution and error-bound to a real symmetric
   * positive-definite banded system of linear equations
   */
  nag_real_sym_posdef_band_lin_solve(order, uplo, n, kd, nrhs, ab, pdab,
                                     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", "Estimate of condition number", "",
              1.0/rcond);

      Vprintf("\n%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%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_POS_DEF)
    {

      /* The matrix A is not positive definite to working precision */

      Vprintf("%s%3ld%s\n\n", "The leading minor of order ",
              fail.errnum, " is not positive definite");
    }
 END:
  if (ab) NAG_FREE(ab);
  if (b) NAG_FREE(b);

  return exit_status;
}

#undef AB
#undef B