Finite Improbability

Well, I have actors working correctly in the game … mostly.

Here’s a screenshot of the test running. That’s 625 actors all maintaining separate locations and an angle. The same class that implements the actors also draws the triangle image oriented correctly, currently they’re following the (not seen) mouse pointer.

The problem I’m running into is that I can get great performance out of this on my dual core macbook. For the most part I can allow all of the actors to run asynchronously without a problem and get about 350 frames/sec. A smaller test (400 actors, also asynchronous) on a creaky old athlon 3000 xp reveals the flaw in that idea: updates don’t have a chance to propogate between render calls, or possibly even between one game loop update and the next. Since this is asynchronous, the only thing I can conclude is that the overhead of managing 400 actors is just too much for that processor. I’m sure I could optimize it a bit, in fact I’m deliberately leaving a lot of the actor code on the “heavy” side so I’ll have some easy targets to optimize it later.

My big concern is that having a second core available is what really makes this whole thing kick ass. Even in scala’s event-based actor mode, which is what I’m using, there are still a few extra threads. Some tests to push the macbook show that my code is using both cores, so the results here just plain don’t translate to a single core system. It would really suck to finish up an awesome game and have it only work with dual core computers.

I’ll probably go through the hassle of trying to package everything for webstart and see if I can get some help testing it, or just run it on every system I can find.

Update:

As was entirely predictible, switching to direct method calls delivered an insane speedup. 7000 ants all adjusting to mouse movement (even if they’re too far away to see any kind of appreciable difference) ran at an acceptable-to-me 33 fps on the macbook. Granted, I’ll have to try it on my “minimum system requirements” box, but I’m happy again.

What I really wanted more than anything out of the actors library was the message passing and pattern matching. Now that I understand it a little better I can fake it pretty well without the overhead of the concurrency. It isn’t even all that hard, I just have to figure out how (or if) I’m going to return values.