perf(stark): skip fixed 0/1 muls in LogUp fingerprint accumulation#696
Merged
Conversation
In the fingerprint hot loop (prover aux-build + constraint-eval + verifier): - Bus-id term: alpha_powers[0] = alpha^0 = 1, so embed the bus id into the extension field directly instead of multiplying by 1 (drops one F*E mul per interaction per row, hoisted out of the row loop on the aux path). - Fixed-zero bus elements (the ~235 constant(0) used for bus-width padding) contribute nothing: skip the F*E multiply + accumulate entirely. Variable elements that happen to be zero on a row also benefit. Value-identical (field addition is exactly associative): stark lib 128/128 (default + parallel), prover bus/logup tests pass, clippy clean. Net effect on prove time is what we want to measure on the 32-core bench.
Collaborator
Author
|
/bench 5 |
Benchmark — ethrex 20 transfers (median of 3)Table parallelism: auto (cores / 3)
Commit: e6524ef · Baseline: cached · Runner: self-hosted bench |
Contributor
|
/bench |
Contributor
|
I have been doing a better statistic analysis for this kind of smaller opts, sharing the results, it's a small speedup but it's there. I will make a follow up to update our measurement methods 
|
- compute_fingerprint_from_step: drop the vestigial *α^0 from the doc
formula so it mirrors the code (and matches docs/cryptography/lookup.md
and spec/logup.typ).
- accumulate_fingerprint{,_from_step}: the zero-skip also covers variable
elements that are zero on a row, not just the constant(0) padding —
reword the inline comments to say so.
This was referenced Jun 25, 2026
MauroToscano
added a commit
that referenced
this pull request
Jun 25, 2026
…agnostics
Confirmed findings from the multi-model review:
- critical/high: SHA-aware binary cache — rebuild when cli_{A,B}.sha don't match
the requested SHAs (was existence-only, so a persistent /tmp on the self-hosted
runner could silently benchmark a previous PR's binaries).
- high: fork-PR head resolution — workflow now resolves headRefOid + fetches
pull/N/head and passes the SHA (origin/<branch> doesn't exist for forks).
- high: clamp /bench-abba N to [2,40] in the workflow (was unbounded -> DoS).
- high: build output -> per-binary log, surfaced on failure (was >/dev/null).
- high: prove runs capture stderr (2>&1) so prover failures are diagnosable.
- medium: add timeout-minutes: 120 so a hang can't strand the bench runner.
- medium: louder warning on git fetch failure.
- low: REF_A is now required (dropped the hardcoded PR #696 default).
- low: fail fast if python3 is missing (before the ~30-min build).
Deliberately kept: shared cargo target across the two worktree builds (incremental
2nd build; cargo recompiles on source change, REBUILD=1 covers dep changes).
…t-constants # Conflicts: # crypto/stark/src/lookup.rs
MauroToscano
approved these changes
Jun 26, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
In the fingerprint hot loop (prover aux-build + constraint-eval + verifier):
Value-identical (field addition is exactly associative): stark lib 128/128 (default + parallel), prover bus/logup tests pass, clippy clean. Net effect on prove time is what we want to measure on the 32-core bench.