31 lines
969 B
Markdown
31 lines
969 B
Markdown
---
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paths:
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- "python/sglang/srt/**/*.py"
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---
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# Mutate ScheduleBatch fields out of place
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Never mutate a `ScheduleBatch` direct field in place — no `.extend()`/`.append()`,
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`+=`/`-=`/`|=`, tensor `.add_()`/`.fill_()`, or slice/index assignment. Build the
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new value and rebind the field:
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```python
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# Bad
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self.reqs.extend(other.reqs)
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self.seq_lens.add_(1)
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self.extend_lens[i] -= encoder_len
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# Good
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self.reqs = self.reqs + other.reqs
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self.seq_lens = self.seq_lens + 1
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lens = self.extend_lens[:]; lens[i] -= encoder_len; self.extend_lens = lens # loop a copy, rebind once
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```
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Why: `copy()` snapshots and the overlap scheduler's queued references rely on old
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objects staying frozen (the prerequisite for the per-step immutable ScheduleBatch
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refactor); derived values like `seq_lens_sum` only recompute safely when fields
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are rebound.
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Out of scope (mutation intended): penalizer buffers, CUDA graph static buffers,
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`ForwardBatch` fields, attention-backend metadata.
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