/* nag_quad_dim1_inf_general (d01rmc) Example Program.
*
* Copyright 2024 Numerical Algorithms Group.
*
* Mark 30.2, 2024.
*/
#include <math.h>
#include <nag.h>
#include <stdio.h>
#ifdef __cplusplus
extern "C" {
#endif
static void NAG_CALL f(const double x[], Integer nx, double fv[],
Integer *iflag, Nag_Comm *comm);
#ifdef __cplusplus
}
#endif
int main(void) {
Integer exit_status = 0;
double bound, result, epsabs, epsrel, abserr, pi;
Integer inf, lrinfo, liinfo, maxsub;
Integer *iinfo = 0;
double *rinfo = 0;
double ruser[1];
/* Nag Types */
NagError fail;
Nag_Comm comm;
INIT_FAIL(fail);
printf("nag_quad_dim1_inf_general (d01rmc) Example Program Results\n\n");
pi = nag_math_pi;
epsabs = 0.0;
epsrel = 1.0e-04;
bound = 0.0;
inf = 1;
maxsub = 20;
lrinfo = 4 * maxsub;
liinfo = MAX(maxsub, 4);
/* Allocate memory */
if (!(rinfo = NAG_ALLOC(lrinfo, double)) ||
!(iinfo = NAG_ALLOC(liinfo, Integer))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* pass constant to f through ruser */
ruser[0] = 4.0 * pi * pi;
comm.user = ruser;
printf("a - lower limit of integration = %11.4f\n", bound);
printf("b - upper limit of integration = infinity\n");
printf("epsabs - absolute accuracy requested = %11.2e\n", epsabs);
printf("epsrel - relative accuracy requested = %11.2e\n", epsrel);
printf("maxsub - maximum number of subintervals = %11" NAG_IFMT "\n",
maxsub);
printf("\n");
/* Evaluate the integral using the vectorized One-dimensional adaptive
* quadrature routine nag_quad_dim1_inf_general (d01rmc).
*/
nag_quad_dim1_inf_general(f, bound, inf, epsabs, epsrel, maxsub, &result,
&abserr, rinfo, iinfo, &comm, &fail);
if (fail.code != NE_NOERROR)
printf("Error or warning from nag_quad_dim1_inf_general (d01rmc) %s\n",
fail.message);
if (fail.code != NE_INT_ARG_LT && fail.code != NE_ALLOC_FAIL &&
fail.code != NE_NO_LICENCE && fail.code != NE_USER_STOP) {
printf("result - approximation to the integral = %11.4f\n", result);
printf("abserr - estimate of the absolute error = %11.2e\n", abserr);
printf("iinfo(0) - number of subintervals used = %11" NAG_IFMT "\n",
iinfo[0]);
} else if (fail.code == NE_USER_STOP) {
printf("Exit requested from f\n");
} else {
exit_status = 1;
goto END;
}
END:
NAG_FREE(rinfo);
NAG_FREE(iinfo);
return exit_status;
}
static void NAG_CALL f(const double x[], Integer nx, double fv[],
Integer *iflag, Nag_Comm *comm) {
Integer i;
/* Set iflag negative to terminate execution for any reason. */
*iflag = 0;
for (i = 0; i < nx; i++)
fv[i] = 1.0 / ((x[i] + 1.0) * sqrt(x[i]));
}