Undo scheduler attempt

[pavpanchekha]

Test https://github.com/paulzzy/egg in Herbie. This is the "Undo Scheduler" described on Zulip which should make egg faster and hopefully also better.

[pavpanchekha]

The unit tests are failing because I didn't update Cargo.lock, no worries there.

[pavpanchekha]

@paulzzy

[pavpanchekha]

Ok, here's the branch results vs baseline. @paulzzy you can use the diff feature to compare them if you'd like. Basically, there's almost no change in either results or runtime, which is a bummer.

This might be because Herbie egraphs are quite small (8k nodes) so perhaps the undo scheduler just never gets a chance to fire, I don't know.

[paulzzy]

Thanks for trying it out! I'll spend some time looking into what's going on

[paulzzy]

I'm surprised the tests passed because I haven't yet implemented support for explanations (which suggests it wasn't actually running, so I'll figure out how to fix that). Are explanations required by Herbie?

[pavpanchekha]

Herbie uses explanations but with them unimplemented I imagine you just return empty explanations? Which Herbie knows to ignore.

[paulzzy]

Currently it just panics with todo! (hence why I know for sure it's not running, because otherwise we'd get a bunch of errors), but if Herbie can accept empty explanations that'll make my life a lot easier :)

[pavpanchekha]

Oh. Huh, then I wonder what this PR even did. Do you want to take a look at teh code? The egg side is tiny / trivial.

[paulzzy]

Currently taking a look! Looks like it panics without explanations being enabled, so I'm figuring out how to bypass that

[pavpanchekha]

@paulzzy I'm going to close this PR, since it's not going to be merged and to keep our PRs clean, but please feel free to fork & make PR when you're ready on your end.

[paulzzy]

Thanks Pavel! I'll submit a PR once I get it working.