Summary

Add no_std support to the o1-utils crate in proof-systems to enable no-std kimchi verifier.

Context

We are working on making the kimchi verifier no_std compatible for embedded and WASM use cases. This requires all dependency crates to support no_std.

Dependency tier: Utility layer (used by poly-commitment and kimchi)

Known blockers

• rayon usage for parallel processing - needs feature gate
• serde_json - needs feature gate
• lazy_cache.rs uses std::sync::Once
• serialization.rs uses std::io::BufReader

Requirements

• Add #![no_std] attribute with conditional std feature
• Add std and alloc features to Cargo.toml
• Feature-gate rayon behind std or parallel feature
• Feature-gate file I/O operations behind std feature
• Replace std::sync::Once with once_cell equivalent
• Replace any std:: imports with core:: or alloc:: equivalents

Tracking

Part of the no-std kimchi initiative. See: o1-labs/proof-systems#3413