Month: August 2023

• Student: eklipsed (Wyatt Radkiewicz)
• Organization: ScummVM
• Mentors: sev, criezy, lephilousophe, ccawley2011, and somean
• Project: Optimize ScummVM Rendering Code
• The 2 Pull Requests:
  • https://github.com/scummvm/scummvm/pull/5243
  • https://github.com/scummvm/scummvm/pull/5144

So originally, the goals for the project were to optimize the pixel blending code in the rendering code for the AGS game engine in ScummVM. The problem was: I completed that goal about half way through the coding period. So me and my mentors talked and what I did after was optimize the rendering code that most other engines in ScummVM use. I used SIMD cpu extensions to net a pretty huge performance gain.

Basically, in the AGS renderer, it got a 5x improvement all around and a 14x improvement in the best scenarios. In the global rendering code for all engines to use it got a 2x improvement all around. Here are the speed up results.

The most challenging part is knowing where to start. First, you must get to know your mentors really good, eg: calls, messaging, etc. If you don’t you’ll be left alone and not knowing what to do. And second, if a coding project seems big you should take three steps.
One: Figure out where you are and the actionable steps you can take to get there. What are the big milestones you have to hit along the way? Do you need to complete something else first to efficiently implement another feature? Should you write tests first? etc.
Two: Get the bare minimum code written. I know that sounds funny, but you should just get stuff working to start. This gives you plenty of time to look at your code and to step three.
Three: Make your code the best code anyones seen. Now that you have 90% of the code written, you can optimize it and make it cleaner and tie up any loose ends like updating the tests, making a PR, etc.

Once again, I’d like to thank Google Summer of Code 2023, ScummVM for the opportunity to work on a project like this and learn so much. And I’d like to thank my mentors for helping me when I was stuck, and teaching me how to work in a team.

So, I’ve updated the AGS blending code to use the new SIMD cpu features detector and added AVX2 support for AGS. All I have left is to get my PR merged, tie up some loose ends, and submit my final submission for GSOC 23. I’ve had a great time coding with my mentors, @criezy, @lephilousophe, @ccawley2011, @somean, and @sev. They have been a great help and very responsive, and it’s been such a blast this past summer coding with them! I’m at college now and got plenty of work ahead of me, so bye!

Last post I talked about how we wanted to continue with what I was doing for the AGS blending code and apply it to the TransparentSurface code (and then eventually move that functionality into ManagedSurface). Well, it seems like I’ve done it! Here’s an overview of what I did: First I didn’t optimize anything but started by refactoring the code and making a ManagedSurface version of TransparentSurfaces’s blit function. Only after I refactored everything to a standard that I thought was pretty good, I started to optimize. After that, I did another round of refactoring and listening to my mentor’s critiques of my code and made the code as clean and fast as I could get it. Not much to show here, everything looks the same as it did before (hopefully lol), but there was a cool bug where sprites were about twice the size they should be, but I didn’t get a picture of it. Anyways, this might be my second or third to last blog post, so its getting to the end here.