perf(crypto): stream field-element bytes into hashers and transcript#773
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Oppen wants to merge 2 commits into
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perf(crypto): stream field-element bytes into hashers and transcript#773Oppen wants to merge 2 commits into
Oppen wants to merge 2 commits into
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Eliminates the per-element heap allocation in Merkle leaf hashing and Fiat-Shamir transcript appends. AsBytes gains a stream_bytes sink method, overridden zero-alloc for Goldilocks base and degree-3 extension; the Merkle backends and DefaultTranscript use it instead of as_bytes()/ to_bytes_be(). Adds hash_data_parts + verify_merkle_path_from_hash so row-pair openings hash two slices directly instead of concatenating them into a throwaway Vec first; verify_composition_poly_opening and FieldElementVectorBackend::hash_data now delegate to their row-pair/parts siblings instead of duplicating the same hashing loop. Recursion guest: single-query 89.7M -> 73.7M cycles, multi-query 2.21B -> 1.82B cycles.
stream_bytes was calling the base-field override three times, one per limb, each landing as its own Digest::update on the guest — three BlockBuffer::digest_blocks + memcpy calls instead of one. Disassembly of the guest ELF showed dyn dispatch itself was fully devirtualized by the #[inline(always)] chain, so the actual cost was the call count, not indirection. Reuse the existing write_bytes_be override (already zero-alloc, byte-identical layout) into a stack buffer and sink once. Recursion guest: single-query 73.9M -> 71.1M cycles, multi-query 1.82B -> 1.78B cycles.
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Summary
AsBytesgains astream_bytessink method, overridden zero-alloc for the Goldilocks base field and its degree-3 extension, replacingas_bytes()/to_bytes_be()returning a freshVec<u8>per element per hash.FieldElementVectorBackend::hash_data_parts+verify_merkle_path_from_hashso row-pair openings (verify_opening_pair,verify_composition_poly_opening,verify_fri_layer_openings) hash two slices directly instead of concatenating them into a throwawayVecfirst;verify_composition_poly_openingandhash_datanow delegate to their row-pair/parts siblings instead of duplicating the hashing loop.stream_byteswas calling the base-field override three times (one per limb), landing as three separateDigest::updatecalls on the guest instead of one. Disassembly confirmed thedyn FnMutsink itself was fully devirtualized (no indirect-call cost), so the actual waste was call count. Now reuses the existing zero-allocwrite_bytes_beoverride into a stack buffer and sinks once.Test plan
cargo test --workspace --exclude math-cuda(492 prover + 137 stark tests, all green) after each commitmake test-ethrexcargo test -p lambda-vm-prover --lib test_recursion_execute_1query -- --ignored --nocapture(in-VM verify accepts, guest commitsvk_digest ‖ output, byte-identical across every change)make test-profile-recursion-single/-multicycle counts confirmed against baseline after each commitllvm-objdump) confirmingstream_bytesdevirtualizes and the extension-field batching removes redundantBlockBuffer::digest_blocks/memcpycalls