Evidence readout
behemoth B=4 ctx=1024 peak memory dropped `27679 MB -> 17816 MB` while step/s moved `0.4 -> 0.3`; tiny memory worsened `161 MB -> 189 MB`
What the attempt taught
Activation recompute is a scale-dependent lever; it should stay opt-in for models where memory, not step time, is the blocker.
Why it stopped or stayed bounded
Checkpointing recovered large-model memory but hurt small-model memory and speed, and the OOMGuard estimator still reports uncheckpointed activation projections.
Method and scope
- Experiment family: runtime perf.
- Record kind: infrastructure.
Disposition
Update memory estimation for `--grad-checkpoint` and consider selective layer checkpointing before broad default use.
This retained disposition is historical evidence, not authorization to restart the experiment. A new run needs a fresh question, frozen evaluator, explicit resource budget, and scoped tracking issue.
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Status and disposition describe what PostTrainLLM retained when this record was indexed. They are not a live product promise, a newly run benchmark, or permission to restart historical work. Unknown or unmeasured fields remain unknown rather than being treated as zero.
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Source provenance
The normalized record comes from docs/attempts.json. The links below are the tracked evidence and explanatory sources preserved with the record.