Very slow compile times

[kevinheavey]

Based on experiments on my machine, the get_poseidon_parameters function lengthens the build time of solana-sdk by 37%. This isn't a mystery since it's 43,000 lines long but I wonder if it can be optimized

[vadorovsky]

I think the best solution for that problem would be to hide the Poseidon functionality in Solana SDK behind a feature flag, so only people interested in ZK would need to build light-poseidon. I'd suggest to open an issue in Solana.

If that idea doesn't get accepted, then I don't think there is anything else we could do, sorry.

I don't think that building parameters can be optimized. These are exactly the same parameters which Circom uses. Providing parameters this way is what other Poseidon libraries do, including:

• the reference implementation - https://extgit.iaik.tugraz.at/krypto/hadeshash/-/blob/master/code/poseidonperm_x5_254_3.sage?ref_type=heads#L10
• arnacube - https://github.com/arnaucube/poseidon-rs/blob/master/src/constants.rs

These parameters could be built either on compile time (which is what we are doing) or could be computed and built during runtime (no, we don't want that in Solana 😅 ). So I think what we are doing now is the best solution, even though it makes the build process longer.