Jack Grigg

We discussed this PR in Halo 2 Office Hours today, and decided that we will not merge it as-is. The core issue is that the serialization format being defined here...

> I'm curious - how do you feel about just using `#[derive(Serialize, Deserialize)]`? That would avoid all of this. That would not solve the above problem, and in fact would...

> The most productive route forward would I think be to work on creating a post-optimisation VerifyingKey struct (the second half of https://github.com/zcash/halo2/issues/643), and then defining an encoding format for...

> > The most productive route forward would I think be to work on creating a post-optimisation VerifyingKey struct (the second half of #643), and then defining an encoding format...

We made some exploratory code changes in Halo 2 Office Hours today, to figure out how to approach the post-optimisation `VerifyingKey` structure. The resulting changes are in https://github.com/zcash/halo2/pull/781, along with...

I made this issue block #5716 because migrating fully to `cxx` will necessitate addressing this issue.

This _might_ be irrelevant now that `shardtree` exists; we will figure this out after 5.4.0 as part of the `lightwalletd` updates.

I forgot to mention that I obtained the above figures by adding the [`--timings` flag](https://doc.rust-lang.org/cargo/reference/timings.html) to `RUST_BUILD_OPTS` in `src/Makefile.am`.

I tried [using `rustc`'s self-profiling](https://fasterthanli.me/articles/why-is-my-rust-build-so-slow#rustc-self-profiling) to figure out where the time was being spent: ```diff diff --git a/src/Makefile.am b/src/Makefile.am index 0e21d2d44c..daecbe9832 100644 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -139,7 +139,7 @@...

I tried combining #6407 with removing `codegen-units` (on my Ryzen 9 5950X): ## `./zcutil/clean.sh && time ./zcutil/build.sh -j30` ### master ``` real 2m52.682s user 6m24.228s sys 0m42.750s ``` ### #6407...