> I don't see a problem with simplifying the exponents first.
Sure, we call that computer algebra. As soon as you start doing that, you aren't doing automatic differentiation, you are doing (at least in part) symbolic differentiation.
Sure, we call that computer algebra. As soon as you start doing that, you aren't doing automatic differentiation, you are doing (at least in part) symbolic differentiation.
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
double f(const double x) {
return pow(x, 1000) / pow(x, 998);
}
int main(int argc, char* argv[]) {
if(argc != 2) {
fprintf(stderr, "Usage: %s x\n", argv[0]);
exit(1);
}
const double x = atof(argv[1]); // demo code without error checking
printf("x = %g, f(x) = %g\n", x, f(x));
exit(0);
}
gcc -Wall -g -o test test.c -lm
petschge@localhost:~$ ./test 0
x = 0, f(x) = -nan
petschge@localhost:~$ ./test 1
x = 1, f(x) = 1
petschge@localhost:~$ ./test 2
x = 2, f(x) = 4
gcc -Wall -O3 -ffast-math -g -o test2 test.c -lm
petschge@localhost:~$ ./test2 0
x = 0, f(x) = 0