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dask chunking tutorial outline #157

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@dcherian

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@dcherian

from the pangeo working meeting discussion with @mgrover1 @jmunroe @norlandrhagen

Here's an outline for an intermediate tutorial talking about dask chunking specifically for Xarray users


Motivation: why care about chunk size?

Keeping track

  • monitoring chunk sizes and num tasks throughout the pipeline using the repr
    • use some images
  • while output blocks may be small (say after a big reduction), intermediate blocks need not be.
  • So keep monitoring chunksizes (and tasks) throughout the pipeline.

Why is it important to choose appropriate chunks early in the pipeline?

  • Demonstrate that rechunking is not cheap in most cases

Specify chunks when reading data

  1. Avoid chunks="auto".
  2. Specifying chunks during data read
    • open_dataset
    • open_mfdataset
  3. Analysis vs storage chunks:
    • Dask chunks should be a multiple of chunks on disk
    • talk about aligning chunks with files stored on disk
    • @djhoese example

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