perf: memoize encoded inner chunk for scalar complete-shard writes#177
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In ShardingCodec._encode_partial_sync's full-shard-rewrite loop, a scalar broadcast value produces byte-for-byte identical results for every complete inner chunk (same fill, same empty-check, same encoded bytes). Compute that outcome once and reuse it across all complete chunks instead of re-merging, re-checking write_empty_chunks, and re-encoding tens of thousands of identical chunks. Incomplete edge chunks still merge against their own data individually. Target case (fused, memory, chunks=100/shards=1M, no compression): write 92.26ms -> 21.59ms (4.3x). Pipeline parity (byte-identical to batched) and 956 tests pass under the fused pipeline; adversarial partial-overwrite/ edge/compression/2D/aliasing checks pass. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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In ShardingCodec._encode_partial_sync's full-shard-rewrite loop, a scalar broadcast value produces byte-for-byte identical results for every complete inner chunk (same fill, same empty-check, same encoded bytes). Compute that outcome once and reuse it across all complete chunks instead of re-merging, re-checking write_empty_chunks, and re-encoding tens of thousands of identical chunks. Incomplete edge chunks still merge against their own data individually.
Target case (fused, memory, chunks=100/shards=1M, no compression): write 92.26ms -> 21.59ms (4.3x). Pipeline parity (byte-identical to batched) and 956 tests pass under the fused pipeline; adversarial partial-overwrite/ edge/compression/2D/aliasing checks pass.
[Description of PR]
TODO:
docs/user-guide/*.mdchanges/