is javascript multithreading possible with IFRAMEs

Question

Hi All,

I'm currently playing with the idea of using IFRAMEs to implement a very simple multithreading engine. However my initial results are showing me that running in threads is slower than just running in a single thread.

My test is:

Single Thread

var start = new Date().getTime();
for (var i = 0; i < 300; i++) { /* Do costly processor operations */ }
debug('Took: ' + new Date().getTime() - start);

Multiple Threads

var start = new Date().getTime();
// In thread 1
for (var i = 0; i < 100; i++) { /* Do costly processor operations */ }
// In thread 2
for (var i = 100; i < 200; i++) { /* Do costly processor operations */ }
// In thread 3
for (var i = 200; i < 300; i++) { /* Do costly processor operations */ }
// In a callback in the original FRAME (thread)
debug('Took: ' + new Date().getTime() - start);

So as can be seen, I'm just splitting the work load amongst IFRAMEs (Note code above is only to give a better picture of what I am doing, it is not working code).

So I'm thinking that even using FRAMEs FireFox still has only one JS engine? Is this assumption correct? (rendering my research stupid), Are other browsers different?

Doing a quick googles I got this article: http://codediaries.blogspot.com/2009/12/real-javascript-multithreading-using.html

However the performance improvements achieved here are more than likely just doing parallel http requests rather than processing power.

Thanks for your insights.

Guido

Answer 1

No, Javascript generally does not support multi-threading. Most interpreters do not have any multi-threading capabilities built-in (just like PHP), probably for portability reasons.

However, since the Rhino engine is written entirely in Java, you may be able to tap into the Thread class, but this would only be feasible if you are doing server-side Javascript.

Answer 2

You could try wrapping your operations in a setTimeout call.

Answer 3

Check out the HTML5 Web Workers Standard to see what JavaScript threading should look like. This is implemented in Firefox 3.5, Safari 4, and Chrome 3, but not IE. If you're willing to require a plugin for IE users and older browsers, check out Google Gears WorkerPool.

Answer 4

Guys,

I've decided on a browser dependant solution. Basically I will use Workers if available, then Gears if available. Finally just single threaded.

Thanks all

Guido