```/* nag_matop_real_gen_matrix_cond_num (f01jbc) Example Program.
*
* Copyright 2014 Numerical Algorithms Group.
*
* Mark 24, 2013.
*/
#include <math.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf01.h>
#include <nagx02.h>
#include <nagx04.h>

#ifdef __cplusplus
extern "C" {
#endif
static void NAG_CALL f(Integer *iflag, Integer nz, const Complex z[],
Complex fz[], Nag_Comm *comm);
#ifdef __cplusplus
}
#endif

#define A(I,J) a[J*pda + I]

int main(void)
{

/* Scalars */
Integer        exit_status = 0;
Integer        i, iflag, j, n, pda;
double         conda, cond_rel, eps, norma, normfa;
/* Arrays */
static double ruser[1] = {-1.0};
double         *a = 0;
/* Nag Types */
Nag_OrderType  order = Nag_ColMajor;
Nag_Comm       comm;
NagError       fail;

INIT_FAIL(fail);

/* Output preamble */
printf("nag_matop_real_gen_matrix_cond_num (f01jbc) ");
printf("Example Program Results\n\n");

/* For communication with user-supplied functions: */
comm.user = ruser;

fflush(stdout);

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

/* Read in the problem size */
scanf("%ld%*[^\n]", &n);

pda = n;
if (!(a = NAG_ALLOC((pda)*(n), double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read in the matrix A from data file */
for (i = 0; i < n; i++)
for (j = 0; j < n; j++) scanf("%lf", &A(i, j));
scanf("%*[^\n] ");

/* Print matrix A using nag_gen_real_mat_print (x04cac)
* Print real general matrix (easy-to-use)
*/
nag_gen_real_mat_print (order, Nag_GeneralMatrix, Nag_NonUnitDiag,
n, n, a, pda, "A", NULL, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_gen_real_mat_print (x04cac)\n%s\n", fail.message);
exit_status = 2;
goto END;
}

/* Find absolute condition number estimate of f(A) for a real matrix A using
* nag_matop_real_gen_matrix_cond_num (f01jbc)
* which uses numerical differentiation.
*/
nag_matop_real_gen_matrix_cond_num (n, a, pda, f, &comm, &iflag,
&conda, &norma, &normfa, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_matop_real_gen_matrix_cond_num (f01jbc)\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* Print absolute condition number estimate */
printf("\nf(A) = cos(2A)\n");
printf("Estimated absolute condition number is: %7.2f\n",conda);

/* nag_machine_precision (x02ajc) The machine precision  */
eps = nag_machine_precision;

/* Find relative condition number estimate */
if ( normfa>eps) {
cond_rel = conda * norma/normfa;
printf("Estimated relative condition number is: %7.2f\n",cond_rel);
}
else {
printf("The estimated norm of f(A) is effectively zero");
printf("and so the relative condition number is undefined.\n");
}

END:
NAG_FREE(a);
return exit_status;
}

static void NAG_CALL f(Integer *iflag, Integer nz, const Complex z[],
Complex fz[], Nag_Comm *comm)
{
/* Scalars */
Integer j;
#pragma omp master
if (comm->user[0] == -1.0)
{
printf("(User-supplied callback f, first invocation.)\n");
comm->user[0] = 0.0;
}
for (j = 0; j < nz; j++) {
/*Complex representation of cos 2z */
fz[j].re =  cos(2.0*z[j].re)*cosh(2.0*z[j].im);
fz[j].im = -sin(2.0*z[j].re)*sinh(2.0*z[j].im);
}
/* Set iflag nonzero to terminate execution for any reason. */
*iflag = 0;
}
```