Vector calculus follow-ups from #1663: eager divergence and a user guide fix - #1732
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rajeeja wants to merge 3 commits into
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Vector calculus follow-ups from #1663: eager divergence and a user guide fix#1732rajeeja wants to merge 3 commits into
rajeeja wants to merge 3 commits into
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The spherical metric term added in #1663 calls `other.values`, which materializes the field and forces the whole divergence to compute eagerly. Its companion in `curl` uses `.data` and stays lazy, so switch divergence to match.
The curl and divergence background cells give the planar formulas, and eight code cells hand-roll the operators out of gradient() components instead of calling curl()/divergence(). Since #1663 the library adds the spherical metric terms, so every worked example demonstrated something the library no longer computes. Add the metric terms to the math, switch the examples to the public API, and rewrite the constant-field discussion: curl and divergence of a constant field are u*tan(lat)/a and -v*tan(lat)/a, not zero. Both are now checked against their closed forms. Residual magnitudes in the prose are corrected to match what the notebook actually prints.
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Closes #1731. Follow-up to #1663 / #1662.
Overview
Two things #1663 left behind.
1.
divergenceis eager on dask input. #1663 added the spherical metric term to bothcurlanddivergence. The two are companions and should behave identically, butdivergencereaches forother.valueswherecurlusesself.data:That materializes
otherand drags the whole divergence eager, socurlanddivergencereturn different types for the same chunked input. The mismatch came in when #1588's.values→.datasweep was applied during a conflict resolution on the #1663 branch and only reached thecurlside.Measured on
test/meshfiles/ugrid/quad-hexagon/grid.ncwith a chunked field:curlArrayArraydivergencendarrayArrayNo test added. Nothing in
test/core/test_vector_calculus.pychunks its input, so the whole gradient/curl/divergence area has no dask coverage to extend; adding just enough scaffolding to pin this one line would be out of proportion to a one-word fix. Worth a separate issue if we want that coverage properly. The existing 38 tests pass unchanged.2.
docs/user-guide/vector_calculus.ipynbstill teaches the planar operators. The curl and divergence background cells givewith no metric term, and eight code cells hand-roll the operators out of
gradient()components instead of callingcurl()/divergence(). So every worked example demonstrated pre-#1663 physics while the library computed something else.This adds the$u\tan\varphi/a$ and $-v\tan\varphi/a$ terms to the math, switches the examples to the public API, and corrects the residual magnitudes quoted in the prose to what the notebook actually prints.
One result changes materially. Curl and divergence of a constant field are no longer exactly zero — they are$u\tan\varphi/a$ and $-v\tan\varphi/a$ , which come to
4.8e-09and9.6e-09on this ±2° MPAS subset. That is correct spherical behaviour, so the notebook now says so and checks both against their closed forms (max deviation0.00e+00) rather than dropping the examples. Everything else moves by less than a part in 10⁴, except the two "≈ 0" residuals which go from2.8e-10to4.0e-09and stay ≈ 0.The notebook is executed by
myst_nbat docs build time and stores no outputs, so its printed numbers were always fresh while the prose around them went stale silently. Every cell was run locally before committing.PR Checklist
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Testing & Benchmarking
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