FA-98207 / Attention mask construction / Member archive
Block-causal mask lets keys cross supplied block boundaries · case 02
Block-causal mask lets keys cross supplied block boundaries.
Case contract
Given nonnegative block lengths, expand owner IDs; visibility is same owner and causal. Zero-length blocks are allowed.
Why this case matters
A small explicit visibility matrix makes sequence-attention boundary behavior reviewable.
One recorded failure
Sample boundary fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| zero block boundary | [[true, false, false, false], [true, true, false, false], [true, true, true, false], [true, true, true, true]] | [[true, false, false, false], [true, true, false, false], [false, false, true, false], [false, false, true, true]] | Failed |
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