Are floating point operations in C associative?

Question

Addition mathematically holds the associative property:

(a + b) + c = a + (b + c)

In the general case, this property does not hold for floa

Answer 1

Floating point multiplication in C is not associative.

In C, Floating point multiplication is not associative.

Some evidence is with this C code:

Pick three random float values.
Check if a*(b*c) is ever not equal to (a*b)*c

#include
#include
#include
using namespace std;
int main() {
    int counter = 0;
    srand(time(NULL));
    while(counter++ < 10){
        float a = rand() / 100000;
        float b = rand() / 100000;
        float c = rand() / 100000;

        if (a*(b*c) != (a*b)*c){
            printf("Not equal\n");
        }
    }
    printf("DONE");
    return 0;
}

The program prints:

Not equal
Not equal
Not equal
Not equal
DONE
RUN FINISHED; exit value 0; real time: 10ms; user: 0ms; system: 0ms

Conclusion:

For my test, three randomly selected floating point multiplication values are associative about 70% of the time.