/* nag_real_sym_posdef_packed_lin_solve (f04bec) 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, n, nrhs, pdb;

  /* Arrays */
  char   uplo[2];
  double *ap=0, *b=0;

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

#ifdef NAG_COLUMN_MAJOR
#define A_UPPER(I,J) ap[J*(J-1)/2 + I - 1]
#define A_LOWER(I,J) ap[(2*n-J)*(J-1)/2 + I - 1]
#define B(I,J) b[(J-1)*pdb + I - 1]
  order = Nag_ColMajor;
#else
#define A_LOWER(I,J) ap[I*(I-1)/2 + J - 1]
#define A_UPPER(I,J) ap[(2*n-I)*(I-1)/2 + J - 1]
#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_packed_lin_solve (f04bec) Example Program"
          " Results\n\n");

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

  Vscanf("%ld%ld%*[^\n] ",   &n,  &nrhs);
  if (n>0 && nrhs >0)
    {
      /* Allocate memory */
      if ( !(ap = NAG_ALLOC(n*(n+1)/2, double)) ||
           !(b = NAG_ALLOC(n*nrhs, double)) )
        {
          Vprintf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
#ifdef NAG_COLUMN_MAJOR
      pdb = n;
#else
      pdb = nrhs;
#endif
    }
  else
    {
      Vprintf("%s\n",   "n and/or nrhs too small");
      exit_status = 1;
      return exit_status;
    }

  Vscanf(" ' %1s '%*[^\n] ", uplo);
  if (*(unsigned char *)uplo == 'L')
    uplo_enum = Nag_Lower;
  else if (*(unsigned char *)uplo == 'U')
    uplo_enum = Nag_Upper;
  else
    {
      Vprintf("Unrecognised character for Nag_UploType type\n");
      exit_status = 1;
      goto END;
    }

  /* Read the upper or lower triangular part of the matrix A from */
  /* data file */

  if (uplo_enum == Nag_Upper)
    {

      for (i = 1; i <= n; ++i)
        {
          for (j = i; j <= n; ++j)
            {
              Vscanf("%lf", &A_UPPER(i,j));
            }
        }
      Vscanf("%*[^\n] ");
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = 1; j <= i; ++j)
            {
              Vscanf("%lf", &A_LOWER(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_packed_lin_solve (f04bec).
   * Computes the solution and error-bound to a real symmetric
   * positive-definite system of linear equations, packed
   * storage
   */
  nag_real_sym_posdef_packed_lin_solve(order, uplo_enum, n, nrhs, ap, 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");
      Vprintf("%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%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 (ap) NAG_FREE(ap);
  if (b) NAG_FREE(b);

  return exit_status;
}

#undef B