/* nag_roots_contfn_cntin (c05awc) Example Program.
*
* Copyright 2024 Numerical Algorithms Group.
*
* Mark 30.1, 2024.
*/
#include <math.h>
#include <nag.h>
#include <stdio.h>
#ifdef __cplusplus
extern "C" {
#endif
static double NAG_CALL f(double x, Nag_Comm *comm);
#ifdef __cplusplus
}
#endif
int main(void) {
/* Scalars */
Integer nfmax, exit_status = 0;
int i;
double eps, eta, x;
/* Arrays */
static double ruser[1] = {-1.0};
NagError fail;
Nag_Comm comm;
printf("nag_roots_contfn_cntin (c05awc) Example Program Results\n");
/* For communication with user-supplied functions: */
comm.user = ruser;
for (i = 3; i <= 4; i++) {
eps = pow(10.0, -i);
x = 1.0;
eta = 0.0;
nfmax = 200;
INIT_FAIL(fail);
/* nag_roots_contfn_cntin (c05awc).
* Locates a zero of a continuous function.
*/
nag_roots_contfn_cntin(&x, eps, eta, f, nfmax, &comm, &fail);
if (fail.code == NE_NOERROR) {
printf("\nWith eps = %10.2e, root is %14.5f\n", eps, x);
} else {
printf("Error from nag_roots_contfn_cntin (c05awc) %s\n", fail.message);
if (fail.code == NE_TOO_MANY_CALLS ||
fail.code == NE_SECANT_ITER_FAILED) {
printf("\nWith eps = %10.2e, final value is %14.5f\n", eps, x);
}
exit_status = 1;
goto END;
}
}
END:
return exit_status;
}
static double NAG_CALL f(double x, Nag_Comm *comm) {
if (comm->user[0] == -1.0) {
printf("(User-supplied callback f, first invocation.)\n");
comm->user[0] = 0.0;
}
return exp(-x) - x;
}