perf(render_shapes): PathCollection of pre-built Paths (avoid per-shape Patch construction)#735
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…e Patch objects (#733) render_shapes (matplotlib) was dominated by constructing one mpatches.Circle/Polygon per shape (each Patch.__init__ resolves default colours via to_rgba + recomputes a transform), then PatchCollection.set_paths converting all N to Paths. Build matplotlib Path objects directly (the form set_paths bakes anyway) and return a PathCollection. Same Paths -> byte-identical; preserves holes (compound paths) and all colour/alpha/outline logic; one code path; no signature change. Apply the coordinate-system affine once to the shared paths (fill + outline collections reference the same Path objects) instead of per-collection, dropping the 4 get_paths loops. End-to-end (300k circles, mpl categorical): ~1.7x faster, ~5.3x lower peak memory. Byte-identical verified: main-vs-branch RGBA == 0 across circles/polygons/multipolygon -with-holes x {categorical, continuous, no-color} x {fill, outline}; plus a guard test that the affine is applied once under a non-identity transform + outline.
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #735 +/- ##
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- Coverage 79.31% 79.26% -0.05%
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Files 17 17
Lines 4607 4596 -11
Branches 1031 1028 -3
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- Hits 3654 3643 -11
Misses 603 603
Partials 350 350
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- circle path: use mpath.Path.circle((x,y), r) instead of hand-rolling unit_circle.vertices*r+center (byte-identical; drops the hoist + comment). - trim narrating/duplicated comments (build docstring, reuse comment) and correct the trans-once comment (the old per-collection transform was redundant work, not a visible double-transform — verified main-vs-branch byte-identical).
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Closes #733.
Problem
render_shapes(matplotlib) is dominated by per-shapePatchconstruction — identical across no-color / categorical / continuous (cProfile, 200k circles, ~23 s):_build_shape_patchesbuilds onempatches.Circle/Polygonper shape (eachPatch.__init__resolves default colors viato_rgba~4×/patch + recomputes a transform), thenPatchCollection.set_pathsconverts all N toPaths.Change
Build
matplotlib.path.Pathobjects directly (the formset_pathsbakes internally anyway) and return aPathCollection:Paths → same backend); preserves holes (compound paths) and all color/alpha/outline logic.Pathobjects), replacing the 4 per-collectionget_paths()loops.Results (end-to-end, 300k circles, matplotlib categorical)
Color-mode-independent (the cost was geometry, not color).
Byte-identity (verified)
main-vs-branch full-canvas RGBA max diff 0 across circles / polygons / multipolygon-with-holes × {categorical, continuous, no-color} × {fill, outline}, identity transform. Plus a guard test that the affine is applied exactly once under a non-identity transform + outline.Datashader +
as_pointspaths untouched (already optimized).