Argthtjtr

Today I decided to play around with WebAssembly for the very first time. So, I wrote this little Fibonacci program in C++:

#include <iostream>

#include <chrono>



int fib(int n) {

    if(n==0) {

        return 0;

    } else if(n==1) {

        return 1;

    } else {

        return fib(n-1) + fib(n-2);

    }

}



int main() {

    std::chrono::high_resolution_clock::time_point t1 = std::chrono::high_resolution_clock::now();

    int sum = 0;



    for (int i = 0; i < 35; ++i) {

        sum += fib(i);

    }



    std::chrono::high_resolution_clock::time_point t2 = std::chrono::high_resolution_clock::now();

    std::chrono::duration<double, std::milli> dur = t2 - t1;



    std::cout << sum << std::endl;

    std::cout << dur.count() << std::endl;

}

And compiled it into Web Assembly (WA from now onwards) using the following command:

emcc fib.cpp -s WASM=1 -o fib.html

Then, after loading the resulting .html file into the browser, the output I got was 14930351 592.8, which means that WA took almost 600 milliseconds.

Then, I wrote a JS equivalent of the same program, as follows:

export function fib(n) {

    return n === 0 ? 0 : (n === 1 ? 1 : fib(n-1) + fib(n-2));

}



export function fibSum(n) {

    let sum = 0;

    for (let i = 0; i < n; i++) {

        sum += fib(i)

    }



    return sum;

}

I used performance.now() to measure the elapsed time in milliseconds to calculate fibSum(35), which gave an output of 347.200 milliseconds on Chrome.

I get it that WA is very new hence the compiler must be missing some optimisations as compared to the V8 engine and it takes time to call WA code from the browser and everything but I was not expecting it to be this slow.

Thoughts? Have I not created a proper test case to compare the two?