Remove a copy in pcolormesh.

anntzer · anntzer · commit be37304ded90 · 2016-07-02T17:24:04.000-07:00
This slightly increases the size of the maximum pcolormesh before
hitting a MemoryError.  Test with

    N = 6000; x, y = mgrid[:N, :N]; z = sin(x + y); pcolormesh(x, y, z)

The patch raises the maximum N to ~8000 on my system (depending on the
load).

OTOH, this probably(?) makes pcolormesh sensitive to later changes in
the input array.
diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
@@ -1741,19 +1741,16 @@ def __init__(self, meshWidth, meshHeight, coordinates,
         Collection.__init__(self, **kwargs)
         self._meshWidth = meshWidth
         self._meshHeight = meshHeight
-        self._coordinates = coordinates
+        # By converting to floats now, we can avoid that on every draw.
+        self._coordinates = np.asarray(coordinates, float).reshape(
+            (meshHeight + 1, meshWidth + 1, 2))
         self._antialiased = antialiased
         self._shading = shading
 
         self._bbox = transforms.Bbox.unit()
         self._bbox.update_from_data_xy(coordinates.reshape(
             ((meshWidth + 1) * (meshHeight + 1), 2)))
 
-        # By converting to floats now, we can avoid that on every draw.
-        self._coordinates = self._coordinates.reshape(
-            (meshHeight + 1, meshWidth + 1, 2))
-        self._coordinates = np.array(self._coordinates, float)
-
     def get_paths(self):
         if self._paths is None:
             self.set_paths()
