tifs-to-geozarr: lower default workers from cpu_count to 4#52
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scottstanie merged 1 commit intoopera-adt:mainfrom Apr 24, 2026
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Default worker count was `min(len(groups), cpu_count())` — 12 on a modern laptop, 16+ on a desktop. Each reader holds one variable (plus its pyramid levels) in RAM until the writer drains it, so peak RSS scales as `(n_workers + 1) × largest_group`. On a typical dolphin stack the largest variable (3D unwrapped / filtered timeseries) is a few GB, and 13 copies is the difference between 20 GB and 90+ GB RSS. Reported by a user on a 96 GB box that still OOMed. Rasterio reads are I/O-bound and release the GIL, so 4 threads already saturate typical disk bandwidth — going higher mostly inflates memory without buying wall time. Users with small variables and plenty of RAM can override via `--workers 12`. Help text updated to make the memory tradeoff explicit. Dropped the now-unused `os` import. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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The problem
User reported
bowser tifs-to-geozarrpeaking at 96 GB RSS on a 12-core laptop with a typical dolphin stack. The(n_workers + 1) × largest_groupbound is being honoured — it's just that the default wasos.cpu_count(), so(12 + 1) × ~7 GB unwrapped stack ≈ 91 GB. Matches the reported number exactly.Fix
Drop the default to 4. That puts the bound at
5 × largest ≈ 35 GB, which fits on any reasonable dev machine.Rationale for 4:
--workers 12for full throughput.Help text on
--workersnow makes the memory tradeoff explicit:Dropped the now-unused
osimport.Test plan
bowser tifs-to-geozarr --helpshows the updated guidance🤖 Generated with Claude Code