FA-98157 / Attention mask construction / Member archive
Sliding window omits the oldest key within its span · case 02
Sliding window omits the oldest key within its span.
Case contract
Return square causal visibility with window W counting the current position; W<=0 yields no visible keys.
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 |
|---|---|---|---|
| window edge | [[true, false, false, false], [false, true, false, false], [false, false, true, false], [false, false, false, true]] | [[true, false, false, false], [true, true, false, false], [false, true, true, false], [false, false, true, true]] | Failed |
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