/* nag_inteq_volterra_weights (d05bwc) Example Program.
*
* Copyright 2024 Numerical Algorithms Group.
*
* Mark 30.0, 2024.
*/
#include <nag.h>
int main(void) {
/* Scalars */
Integer exit_status = 0;
Integer i, iorder, j, nomg, p, n;
char methodstring[10];
/* Arrays */
double *omega = 0, *sw = 0;
/* NAG types */
NagError fail;
Nag_ODEMethod method;
INIT_FAIL(fail);
printf("nag_inteq_volterra_weights (d05bwc) Example Program Results\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%9s%*[^\n] ", methodstring);
/*
* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value.
*/
method = (Nag_ODEMethod)nag_enum_name_to_value(methodstring);
scanf("%" NAG_IFMT "%*[^\n] ", &iorder);
scanf("%" NAG_IFMT "%*[^\n] ", &nomg);
switch (method) {
case Nag_Adams:
p = iorder - 1;
break;
case Nag_BDF:
p = iorder;
break;
}
n = nomg + p - 1;
if (!(omega = NAG_ALLOC(nomg, double)) || !(sw = NAG_ALLOC(p * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/*
nag_inteq_volterra_weights (d05bwc).
Generate weights for use in solving Volterra equations.
*/
nag_inteq_volterra_weights(method, iorder, nomg, omega, sw, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_inteq_volterra_weights (d05bwc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
printf("\nThe convolution weights\n\n n-j omega\n");
for (j = 0; j < nomg; j++)
printf("%3" NAG_IFMT " %10.4f\n", j + 1, omega[j]);
printf("\nThe weights W\n");
printf("\n i ");
for (j = 0; j < p; j++)
printf("%11s%" NAG_IFMT " ", "j = ", j);
printf("\n");
#define SW(I, J) sw[J * n + I]
for (i = 0; i < n; i++) {
printf("%3" NAG_IFMT "", i + 1);
for (j = 0; j < p; j++)
printf("%13.4f", SW(i, j));
printf("\n");
}
#undef SW
END:
NAG_FREE(sw);
NAG_FREE(omega);
return exit_status;
}