NAG Library Manual, Mark 30.1
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_sparse_complex_gen_solve_jacssor (f11dsc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.1, 2024.
 */
#include <nag.h>
int main(void) {
  /* Scalars */
  Integer exit_status = 0;
  double omega, rnorm, tol;
  Integer i, itn, m, maxitn, n, nnz;
  /* Arrays */
  Complex *a = 0, *b = 0, *x = 0;
  Integer *icol = 0, *irow = 0;
  char nag_enum_arg[40];
  /* NAG types */
  Nag_SparseNsym_Method method;
  Nag_SparseNsym_PrecType precon;
  NagError fail;

  INIT_FAIL(fail);

  printf(
      "nag_sparse_complex_gen_solve_jacssor (f11dsc) Example Program Results\n\n");
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "%*[^\n]", &n);
  scanf("%" NAG_IFMT "%*[^\n]", &nnz);
  scanf("%39s%*[^\n]", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  method = (Nag_SparseNsym_Method)nag_enum_name_to_value(nag_enum_arg);
  scanf("%39s%*[^\n]", nag_enum_arg);
  precon = (Nag_SparseNsym_PrecType)nag_enum_name_to_value(nag_enum_arg);
  scanf("%lf%*[^\n]", &omega);
  scanf("%" NAG_IFMT "%lf%" NAG_IFMT "%*[^\n]", &m, &tol, &maxitn);
  if (!(a = NAG_ALLOC((nnz), Complex)) || !(b = NAG_ALLOC((n), Complex)) ||
      !(x = NAG_ALLOC((n), Complex)) || !(icol = NAG_ALLOC((nnz), Integer)) ||
      !(irow = NAG_ALLOC((nnz), Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }
  /* Read the matrix A */
  for (i = 0; i < nnz; i++)
    scanf(" ( %lf , %lf ) %" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &a[i].re,
          &a[i].im, &irow[i], &icol[i]);
    /* Read rhs vector b and initial approximate solution x */
  for (i = 0; i < n; i++)
    scanf(" ( %lf , %lf ) ", &b[i].re, &b[i].im);
  scanf("%*[^\n]");
  for (i = 0; i < n; i++)
    scanf(" ( %lf , %lf ) ", &x[i].re, &x[i].im);

  /* solve ax = b */
  /* nag_sparse_complex_gen_solve_jacssor (f11dsc).
   * Solution of complex sparse non-Hermitian linear system, RGMRES, CGS,
   * Bi-CGSTAB or TFQMR method, Jacobi or SSOR preconditioner Black Box.
   */
  nag_sparse_complex_gen_solve_jacssor(method, precon, n, nnz, a, irow, icol,
                                       omega, b, m, tol, maxitn, x, &rnorm,
                                       &itn, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_sparse_complex_gen_solve_jacssor (f11dsc).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
  printf("Converged in%13" NAG_IFMT " iterations\n", itn);
  printf("Final residual norm = %11.3e\n\n", rnorm);
  /* Output x */
  printf("%14s\n", "Solution");
  for (i = 0; i < n; i++)
    printf("(%13.4e, %13.4e)\n", x[i].re, x[i].im);

END:
  NAG_FREE(a);
  NAG_FREE(b);
  NAG_FREE(x);
  NAG_FREE(icol);
  NAG_FREE(irow);
  return exit_status;
}