/* 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(int argc, char *argv[])
{
  FILE          *fpin, *fpout;
  char          *outfile = 0;
  /* Scalars */
  double        errbnd, rcond;
  Integer       exit_status, i, j, n, nrhs, pdb;

  /* Arrays */
  char          nag_enum_arg[40];
  double        *ap = 0, *b = 0;

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

#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);

  /* 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_real_sym_posdef_packed_lin_solve (f04bec) Example "
          "Program Results\n\n");

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

  fscanf(fpin, "%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)))
        {
          fprintf(fpout, "Allocation failure\n");
          exit_status = -1;
          goto END;
        }
#ifdef NAG_COLUMN_MAJOR
      pdb = n;
#else
      pdb = nrhs;
#endif
    }
  else
    {
      fprintf(fpout, "%s\n", "n and/or nrhs too small");
      exit_status = 1;
      return exit_status;
    }

  fscanf(fpin, "%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);

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

  if (uplo == Nag_Upper)
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = i; j <= n; ++j)
            {
              fscanf(fpin, "%lf", &A_UPPER(i, j));
            }
        }
      fscanf(fpin, "%*[^\n] ");
    }
  else
    {
      for (i = 1; i <= n; ++i)
        {
          for (j = 1; j <= i; ++j)
            {
              fscanf(fpin, "%lf", &A_LOWER(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] ");

  /* 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, 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)
       */
      if (outfile) fclose(fpout);
      nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                             nrhs, b, pdb, "Solution", 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;
        }
      fprintf(fpout, "\n");
      fprintf(fpout, "%s\n%6s%10.1e\n\n\n", "Estimate of condition number", "",
              1.0/rcond);
      fprintf(fpout, "%s\n%6s%10.1e\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 */
      fprintf(fpout, "\n%s\n%6s%10.1e\n\n\n",
              "Estimate of reciprocal of condition number", "", rcond);

      /* nag_gen_real_mat_print (x04cac), see above. */
      if (outfile) fclose(fpout);
      nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                             nrhs, b, pdb, "Solution", 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;
        }
    }
  else if (fail.code == NE_POS_DEF)
    {
      /* The matrix A is not positive definite to working precision */
      fprintf(fpout, "%s%3ld%s\n\n", "The leading minor of order ",
              fail.errnum, " is not positive definite");
    }
  else
    {
      fprintf(fpout, "Error from "
              "nag_real_sym_posdef_packed_lin_solve (f04bec).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }
 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  if (ap) NAG_FREE(ap);
  if (b) NAG_FREE(b);

  return exit_status;
}