Running async processes in node.js on multiple cores
Notice a pattern in the array of your async.parallel call? All the functions are the same except for a single number. 

And, judging by the repeated comment for each function, you just copied the first version of the function and changed that one number.

You should create a loop that pushes functions into the array, changing that single number each time.

for(var i = 0; i &lt; 4; i++) {
    array.push(function(callback) {
        console.log(i + 1);
        var k = cp.fork('./doOther.js',['0' + (i + 1)]);
        k.on('message',function(msg){
            console.log(msg);
            callback();
        });
    }
}


As another tip, if you aren't going to use k again, don't store cp.form(...,...); in a variable; just continue the .on stuff that you were doing to the k but to the cp.form(...,...).

That would look like this:

cp.fork('./doOther.js', ['0' + (i + 1)]).on('message', function(msg) {
    console.log(msg)
    callback();
});




Other than that, I'm not too familiar with node.js and what a core is, so I can't help you on that part.