Green Threads
This is a small framework I wrote that addresses some of the issues associated with ActionScript being executed linearly in one thread. If the language offered an API for threading, computationally expensive routines could be run in a separate thread, keeping the application’s UI appropriately responsive.
The idea is to offer a simple means to decompose:
- deep recursion
- large loops
- computationally expensive tasks
I’ve created 2 demos (FP10) to illustrate the issue.
The first demo is an implementation of the A* algorithm. If you select to execute the path-finding normally, you’ll notice the Flex UI becomes unresponsive; if you’re lucky, you might even get the spinning beach ball of death. But when you run the algorithm in a green thread, the application UI remains responsive. Select start and end nodes at diagonally opposite corners to force the algorithm through a lot of work.
The second demo encodes 3 images. This is a little harder to visualize in a demo, so here’s what’s happening: I take an embedded image, encode it as a .png 3 times and then decode and render the ByteArray to show the encoding’s success. As with the path-finding demo, you’ll see the UI become unresponsive when you run the encoding normally. But decomposed to run over a few seconds, everything runs well.
A thread’s chief responsibility, aside from running its processes, is to maintain frame rate. The API offers the user the ability to set execution frequency and processing share (percentage). It polices itself according to these allocation constraints. If a process exceeds its allotment, it is penalized in the next cycle. This works surprisingly well to maintain frame rate and adhere to the user’s request.
The source is pretty well commented and should be easy to implement! And if nothing else, there’s an object-oriented implementation of the A* algorithm… (based on Ian Millington’s pseudo code in his Artificial Intelligence For Games).
I started this framework because of (and got the name from) my awesome friend, Roger Braunstein, who shared his elegant and simple solution with me a couple months ago, and referenced the obscure deprecated Java API.