metal: drop the MFA triangular-constant probe test- fails on M1 Pro (macOS 26.5.2) and an M4 (macOS 26.6). - #2546
Open
czoli1976 wants to merge 1 commit into
Open
metal: drop the MFA triangular-constant probe test- fails on M1 Pro (macOS 26.5.2) and an M4 (macOS 26.6).#2546czoli1976 wants to merge 1 commit into
czoli1976 wants to merge 1 commit into
Conversation
The test asserted that the MFA `triangular` function constant alone does not mask, which stopped holding on macOS 26.5: the probe now sees causal output and the metal suite fails there. Nothing depends on that behaviour - MetalMfaSdpa always passes the constant as false and realizes causal as a bottom-right aligned additive mask - so the probe only pinned a driver detail. Drop it, and cover the cases that do matter with causal Sq != Sk and a decode step against a cache. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This was referenced Aug 1, 2026
czoli1976
changed the title
czoli1976
changed the title
This was referenced Aug 1, 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
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
test_mfa_attention_causal_const_is_noopfails on macOS 26.5 — the probe itlocks down (MFA's
triangularfunction constant alone does not mask) no longerholds there, so
cargo test -p tract-metalis red on that OS:Nothing in tract depends on it:
MetalMfaSdpapasses the constant asfalseand realizes causal as a bottom-right aligned
[Sq,Sk]additive mask, so thetest only pinned a driver detail that Apple has since changed. This drops it and
spends the coverage where it matters instead —
test_metal_mfa_sdpa_opgainscausal with
Sq != Skand a decode step against a cache, both of which thesuite was missing. Both are bit-exact against the host reference here
(
max_abs=0.000000), i.e. the fused path itself is fine on macOS 26.5.Not one machine's quirk: the probe fails with the same numbers on an M1 Pro
(macOS 26.5.2) and an M4 (macOS 26.6).
No behaviour change.
cargo test -p tract-metal --releaseon the M1 Pro:76 passed, 0 failed (was 1 failed); fmt and clippy clean.
🍍