output.txt

primality test using primality_sqrt_bound(int64_t)
L = 100000000 : R = 100100000
test 1 duration : 0.761 s
test 2 duration : 0.762 s
test 3 duration : 0.764 s
test 4 duration : 0.771 s
test 5 duration : 0.741 s
test 6 duration : 0.741 s
test 7 duration : 0.769 s
test 8 duration : 0.744 s
test 9 duration : 0.737 s
test 10 duration : 0.741 s
average of 10 test(s) : 0.7531 s

primality_sqrt_bound.cpp

#include <cmath>

bool primality_sqrt_bound(int64_t a) {
    double lim = sqrt(a);
    for(int i = 2; i <= lim; i++)
        if(a % i == 0)
            return false;
    return true;
}