ex01_basic.md

Running a simple function in a thread

This first example demonstrates how you can run an expensive computation in a worker thread and obtain its result.

First, we define the function that we want to execute in the worker thread:

function fibo(n) {
	return n > 1 ? fibo(n - 1) + fibo(n - 2) : 1;
}

Then, we create a worker thread with the Threads.create call:

var Threads = require('threads_a_gogo');
var t = Threads.create();

In the next step, we load the function into the worker thead. We get the function's source with fibo.toString() and we call t.eval(source) to evalutate it into the worker thread's context:

t.eval(fibo);

Now, we are ready to call this function. We use the t.eval function again, with two arguments this time.
The first argument is the expression to evaluate.
The second one is a callback that receives the result (or an error if there was one).

t.eval('fibo(10)', function(err, result) {
	if (err) throw err; // something abnormal
	// print the result
	console.log('fibo(10)=' + result);
	// chain with next step
	step2();
});

Let's call it again:

function step2() {
	t.eval('fibo(20)', function(err, result) {
		if (err) throw err;
		console.log('fibo(20)=' + result);
		step3();
	});
}

If the expression is invalid, we get an error through the callback

function step3() {
	// 'x' is not defined
	t.eval('fibo(x)', function(err, result) {
		console.log('error=' + err);
		step4();
	});
}

But the thread is still alive and ready to accept more calls:

function step4() {
	t.eval('fibo(15)', function(err, result) {
		console.log('fibo(15)=' + result);
		step5();
	});
}

Once we are done, we destroy the thread:

function step5() {
	t.destroy();
}

Output

fibo(10)=89
fibo(20)=10946
error=Error: ReferenceError: x is not defined
fibo(15)=987