Reorder channelwise gated delta rule chunked hot loops for autovectorization (#21021)#21021
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Reorder channelwise gated delta rule chunked hot loops for autovectorization (#21021)#21021JakeStevens wants to merge 2 commits into
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🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/21021
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…ization (pytorch#21021) Summary: Reorder the chunked prefill inner loops (steps 1, 4, 5, 6) so the innermost loop runs contiguously over the head dimension (k or v) instead of striding down a column of the state / pv. This lets the compiler autovectorize the now-unit-stride AXPYs; hand-written at::vec was tried and was slower than the compiler output, so the loops stay scalar. Differential Revision: D112598714
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…ization (pytorch#21021) Summary: Reorder the chunked prefill inner loops (steps 1, 4, 5, 6) so the innermost loop runs contiguously over the head dimension (k or v) instead of striding down a column of the state / pv. This lets the compiler autovectorize the now-unit-stride AXPYs; hand-written at::vec was tried and was slower than the compiler output, so the loops stay scalar. Reviewed By: billmguo Differential Revision: D112598714
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…ization (pytorch#21021) Summary: Reorder the chunked prefill inner loops (steps 1, 4, 5, 6) so the innermost loop runs contiguously over the head dimension (k or v) instead of striding down a column of the state / pv. This lets the compiler autovectorize the now-unit-stride AXPYs; hand-written at::vec was tried and was slower than the compiler output, so the loops stay scalar. Reviewed By: billmguo Differential Revision: D112598714
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…ization (pytorch#21021) Summary: Reorder the chunked prefill inner loops (steps 1, 4, 5, 6) so the innermost loop runs contiguously over the head dimension (k or v) instead of striding down a column of the state / pv. This lets the compiler autovectorize the now-unit-stride AXPYs; hand-written at::vec was tried and was slower than the compiler output, so the loops stay scalar. Reviewed By: billmguo Differential Revision: D112598714
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…h#21061) Summary: Route the channelwise gated delta rule by sequence length: T == 1 keeps the two-pass token recurrence for autoregressive decode, while T != 1 uses a chunkwise WY/UT formulation for prefill. The chunked path computes per-channel log-decay prefixes, causal query/key terms, the beta-folded triangular transform, WY pseudo-keys and pseudo-values, and inter-chunk state carry. It handles a ragged final chunk without a separate tail implementation. Parallelize independent (batch, head) work across the ExecuTorch threadpool. Each worker receives a disjoint slice of one temporary scratch arena, avoiding shared mutable buffers while amortizing allocation across chunks. Reviewed By: billmguo Differential Revision: D112597348
…ization (pytorch#21021) Summary: Reorder the chunked prefill inner loops (steps 1, 4, 5, 6) so the innermost loop runs contiguously over the head dimension (k or v) instead of striding down a column of the state / pv. This lets the compiler autovectorize the now-unit-stride AXPYs; hand-written at::vec was tried and was slower than the compiler output, so the loops stay scalar. Reviewed By: billmguo Differential Revision: D112598714
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Summary:
Reorder the chunked prefill inner loops (steps 1, 4, 5, 6) so the innermost loop runs contiguously over the head dimension (k or v) instead of striding down a column of the state / pv. This lets the compiler autovectorize the now-unit-stride AXPYs; hand-written at::vec was tried and was slower than the compiler output, so the loops stay scalar.
Reviewed By: billmguo
Differential Revision: D112598714