NAG Library Manual, Mark 27.3
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_sparse_complex_herm_matvec (f11xsc) Example Program.
 *
 * Copyright 2021 Numerical Algorithms Group.
 *
 * Mark 27.3, 2021.
 */

#include <nag.h>

int main(void) {
  /* Scalars */
  Integer exit_status = 0;
  Integer i, j, n, nnz;
  /* Arrays */
  char nag_enum_arg[40];
  Integer *irow = 0, *icol = 0;
  Complex *a = 0, *x = 0, *y = 0;
  /* NAG types */
  NagError fail;
  Nag_SparseSym_CheckData check;

  INIT_FAIL(fail);

  printf("nag_sparse_complex_herm_matvec (f11xsc) Example Program Results\n");

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

  /* Read order of matrix and number of nonzero entries */
  scanf("%" NAG_IFMT "%*[^\n]", &n);
  scanf("%" NAG_IFMT "%*[^\n]", &nnz);

  /* Allocate memory */
  if (!(a = NAG_ALLOC(nnz, Complex)) || !(x = NAG_ALLOC(n, Complex)) ||
      !(y = 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 the vector x */
  for (j = 0; j < n; j++)
    scanf(" ( %lf , %lf ) ", &x[j].re, &x[j].im);
  scanf("%*[^\n]");

  /* Calculate matrix-vector product */
  /* Nag_SparseSym_Check */
  scanf("%39s%*[^\n]", nag_enum_arg);
  check = (Nag_SparseSym_CheckData)nag_enum_name_to_value(nag_enum_arg);

  /* nag_sparse_complex_herm_matvec (f11xsc)
   * Complex sparse Hermitian matrix vector multiply.
   */
  nag_sparse_complex_herm_matvec(n, nnz, a, irow, icol, check, x, y, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_sparse_complex_herm_matvec (f11xsc)\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }

  /* Output results */
  printf(" Matrix-vector product\n");
  for (j = 0; j < n; j++)
    printf(" (%13.4e, %13.4e)\n", y[j].re, y[j].im);

END:
  NAG_FREE(a);
  NAG_FREE(x);
  NAG_FREE(y);
  NAG_FREE(icol);
  NAG_FREE(irow);

  return exit_status;
}