fibtest.cpp

#include <iostream>
#include <chrono>

uint64_t fib(uint64_t n) {
        uint64_t a=1;
        uint64_t b=1;
        uint64_t c = b+a;
        for (uint64_t i=0; i<(n-2); ++i) {
                c = b + a;
                b = a;
                a = c;
        }
        return c;
}

int main(int argc, char *argv[]) {
        const auto times = 10000000;
        volatile uint64_t myval = 0;
        auto start =  std::chrono::system_clock::now();
        for (auto i=0; i < times; ++i) {
                myval = fib(78);
        }
        auto stop =  std::chrono::system_clock::now();
        std::chrono::duration<double> elapsed = stop - start;
        std::cout << "fib(78) = " << myval << " took " << elapsed.count() << " seconds." << std::endl;
}