This has been a massive success!
So I left 32x GPT 5.5 agents (enough to fill the 5h limit) on 32 separate machines. Each one received HVM5's unoptimized file, and a prompt demanding for a 10x speedup. After 4 rounds, all agents reached ~2x speedups, with 1.3x to 2x increases in file sizes.
Many cool ideas surfaced. Some are obvious and most agents rediscovered to them, like computed gotos. But others are actually surprising. For example, turns out a bounded LIFO freelist is MUCH faster than the usual algorithm. Many agents didn't bother trying. Neither did I!
Now I'm in the process of mining insights from the 32 runs so I can merge them into a "super HVM5". Not sure what is the best way to do this, and my 200x credits are about to expire, but I still have a few hours, so I have one shot at getting it right. Sounds fun!
(Also thanks for the free credits, I appreciate it a lot...)