For examlpe, if I change a test to use `ConstantArityBits(4, 5)`, I get
To efficiently perform FRI checks with an arity of 16, at least 152 wires are needed. Consider reducing arity.
* Automatically select FRI reduction arities
This way when a proof's degree changes, we won't need to manually update the `FriConfig`s of any recursive proofs on top of it.
For now I've added two methods of selecting arities. The first, `ConstantArityBits`, just applies a fixed reduciton arity until the degree has shrunk below a certain threshold. The second, `MinSize`, searches for the sequence of arities that minimizes proof size.
Note that this optimization is approximate -- e.g. it doesn't account for the effect of compression, and doesn't count some minor contributions to proof size, like the Merkle roots from the commit phase. It also assumes we're not using Merkle caps in serialized proofs, and that we're inferring one of the evaluations, even though we haven't made those changes yet.
I think we should generally use `ConstantArityBits` for proofs that we will recurse on, since using a single arity tends to be more recursion-friendly. We could use `MinSize` for generating final bridge proofs, since we won't do further recursion on top of those.
* Fix tests
* Feedback
* Disable ZK in large_config
Speeds up the tests from ~6m to ~1m (debug mode). `large_config` is crate-private so I don't think we need to worry about real users forgetting ZK, and I don't think ZK seems important in these tests, though we should probably have ZK enabled for a couple tests.
A couple tests need ZK or they fail; I added a TODO to look later.
This led to a few other changes:
- Fixed a bug where `trim` could truncate the final poly to a non-power-of-two length. This was improbable when ZK is on due to randomization.
- Gave a few methods access to the whole `CircuitConfig` vs `FriConfig` -- sort of necessary for the above fix, and I don't think there's much downside.
- Remove `cap_height` from `FriConfig` -- didn't really need it any more after giving more methods access to `CircuitConfig`, and having a single copy of the param feels cleaner/safer to me.
* PR feedback
No functional changes here. The biggest change was moving certain files into new directories like `plonk` and `iop` (for things like `Challenger` that could be used in STARKs or other IOPs). I also split a few files, renames, etc, but again nothing functional, so I don't think a careful review is necessary (just a sanity check).
* Make ZK optional
* Remove rate from FriConfig
Seems redundant, and we've had some tests break due to the two fields not matching.
* zero_knowledge: false in bench
