Optimize VectorField min distance calculation (#2314)

holoviews/plotting/bokeh/chart.py

@@ -171,17 +171,18 @@ class VectorFieldPlot(ColorbarPlot):
     def _get_lengths(self, element, ranges):
         mag_dim = element.get_dimension(self.size_index)
         (x0, x1), (y0, y1) = (element.range(i) for i in range(2))
-        base_dist = get_min_distance(element)
         if mag_dim:
             magnitudes = element.dimension_values(mag_dim)
             _, max_magnitude = ranges[mag_dim.name]
             if self.normalize_lengths and max_magnitude != 0:
                 magnitudes = magnitudes / max_magnitude
             if self.rescale_lengths:
+                base_dist = get_min_distance(element)
                 magnitudes *= base_dist
         else:
             magnitudes = np.ones(len(element))
             if self.rescale_lengths:
+                base_dist = get_min_distance(element)
                 magnitudes *= base_dist
 
         return magnitudes

holoviews/plotting/mpl/chart.py

@@ -605,16 +605,6 @@ class VectorFieldPlot(ColorbarPlot):
 
     _plot_methods = dict(single='quiver')
 
-    def __init__(self, *args, **params):
-        super(VectorFieldPlot, self).__init__(*args, **params)
-        self._min_dist = self._get_map_info(self.hmap)
-
-
-    def _get_map_info(self, vmap):
-        """
-        Get the minimum sample distance and maximum magnitude
-        """
-        return np.min([get_min_distance(vfield) for vfield in vmap])
 
 
     def get_data(self, element, ranges, style):
@@ -627,7 +617,8 @@ def get_data(self, element, ranges, style):
         if self.invert_axes: radians = radians+1.5*np.pi
         angles = list(np.rad2deg(radians)) 
         if self.rescale_lengths:
-            input_scale = input_scale / self._min_dist
+            min_dist = get_min_distance(element)
+            input_scale = input_scale / min_dist
 
         mag_dim = element.get_dimension(self.size_index)
         if mag_dim:

holoviews/plotting/util.py

@@ -1,6 +1,8 @@
 from __future__ import unicode_literals, absolute_import
+
 from collections import defaultdict
 import traceback
+import warnings
 
 import numpy as np
 import param
@@ -549,19 +551,32 @@ def traverse_setter(obj, attribute, value):
     obj.traverse(lambda x: setattr(x, attribute, value))
 
 
+def _get_min_distance_numpy(element):
+    """
+    NumPy based implementation of get_min_distance
+    """
+    xys = element.array([0, 1])
+    with warnings.catch_warnings():
+        warnings.filterwarnings('ignore', r'invalid value encountered in')
+        xys = xys.astype('float32').view(np.complex64)
+        distances = np.abs(xys.T-xys)
+        np.fill_diagonal(distances, np.inf)
+        distances = distances[distances>0]
+        if len(distances):
+            return distances.min()
+    return 0
+
+
 def get_min_distance(element):
     """
     Gets the minimum sampling distance of the x- and y-coordinates
     in a grid.
     """
-    xys = element.array([0, 1]).astype('float64').view(dtype=np.complex128)
-    m, n = np.meshgrid(xys, xys)
-    distances = np.abs(m-n)
-    np.fill_diagonal(distances, np.inf)
-    distances = distances[distances>0]
-    if len(distances):
-        return distances.min()
-    return 0
+    try:
+        from scipy.spatial.distance import pdist
+        return pdist(element.array([0, 1])).min()
+    except:
+        return _get_min_distance_numpy(element)
 
 
 def rgb2hex(rgb):

tests/testplotutils.py → tests/plotting/testplotutils.py

@@ -1,3 +1,5 @@
+from __future__ import absolute_import
+
 from unittest import SkipTest
 from nose.plugins.attrib import attr
 
@@ -12,7 +14,7 @@
 from holoviews.operation import operation
 from holoviews.plotting.util import (
     compute_overlayable_zorders, get_min_distance, process_cmap,
-    initialize_dynamic, split_dmap_overlay)
+    initialize_dynamic, split_dmap_overlay, _get_min_distance_numpy)
 from holoviews.streams import PointerX
 
 try:
@@ -430,13 +432,12 @@ class TestPlotColorUtils(ComparisonTestCase):
     def test_process_cmap_mpl(self):
         colors = process_cmap('Greys', 3)
         self.assertEqual(colors, ['#ffffff', '#959595', '#000000'])
-
 
     def test_process_cmap_instance_mpl(self):
         try:
             from matplotlib.cm import get_cmap
         except:
-            raise SkipError("Matplotlib needed to test matplotlib colormap instances")
+            raise SkipTest("Matplotlib needed to test matplotlib colormap instances")
         cmap = get_cmap('Greys')
         colors = process_cmap(cmap, 3)
         self.assertEqual(colors, ['#ffffff', '#959595', '#000000'])
@@ -478,6 +479,20 @@ def test_get_min_distance_int32_type(self):
         dist = get_min_distance(Points((X.flatten(), Y.flatten())))
         self.assertEqual(dist, 1.0)
 
+    def test_get_min_distance_float32_type_no_scipy(self):
+        xs, ys = (np.arange(0, 2., .2, dtype='float32'),
+                  np.arange(0, 2., .2, dtype='float32'))
+        X, Y = np.meshgrid(xs, ys)
+        dist = _get_min_distance_numpy(Points((X.flatten(), Y.flatten())))
+        self.assertEqual(dist, np.float32(0.2))
+
+    def test_get_min_distance_int32_type_no_scipy(self):
+        xs, ys = (np.arange(0, 10, dtype='int32'),
+                  np.arange(0, 10, dtype='int32'))
+        X, Y = np.meshgrid(xs, ys)
+        dist = _get_min_distance_numpy(Points((X.flatten(), Y.flatten())))
+        self.assertEqual(dist, 1.0)
+
 
 @attr(optional=1)  # Flexx is optional
 class TestBokehUtils(ComparisonTestCase):