Add support for fast QuadMesh rasterization (#4020)

holoviews/core/data/__init__.py

@@ -990,13 +990,17 @@ def to(self):
         return self._conversion_interface(self)
 
 
-    def clone(self, data=None, shared_data=True, new_type=None, *args, **overrides):
+    def clone(self, data=None, shared_data=True, new_type=None, link=True,
+              *args, **overrides):
         """Clones the object, overriding data and parameters.
 
         Args:
             data: New data replacing the existing data
             shared_data (bool, optional): Whether to use existing data
             new_type (optional): Type to cast object to
+            link (bool, optional): Whether clone should be linked
+                Determines whether Streams and Links attached to
+                original object will be inherited.
             *args: Additional arguments to pass to constructor
             **overrides: New keyword arguments to pass to constructor
 
@@ -1010,6 +1014,12 @@ def clone(self, data=None, shared_data=True, new_type=None, *args, **overrides):
         if data is None:
             overrides['_validate_vdims'] = False
 
+            # Allows datatype conversions
+            if shared_data:
+                data = self
+                if link:
+                    overrides['plot_id'] = self._plot_id
+
             if 'dataset' not in overrides:
                 overrides['dataset'] = self.dataset
 

holoviews/core/data/interface.py

@@ -7,7 +7,7 @@
 
 from .. import util
 from ..element import Element
-from ..ndmapping import OrderedDict, NdMapping
+from ..ndmapping import NdMapping
 
 
 def get_array_types():
@@ -225,14 +225,19 @@ def initialize(cls, eltype, data, kdims, vdims, datatype=None):
                 if not datatype:
                     datatype = eltype.datatype
 
-            if data.interface.datatype in datatype and data.interface.datatype in eltype.datatype:
+            interface = data.interface
+            if interface.datatype in datatype and interface.datatype in eltype.datatype:
                 data = data.data
-            elif data.interface.gridded and any(cls.interfaces[dt].gridded for dt in datatype):
-                gridded = OrderedDict([(kd.name, data.dimension_values(kd.name, expanded=False))
-                                       for kd in data.kdims])
+            elif interface.gridded and any(cls.interfaces[dt].gridded for dt in datatype):
+                new_data = []
+                for kd in data.kdims:
+                    irregular = interface.irregular(data, kd)
+                    coords = data.dimension_values(kd.name, expanded=irregular,
+                                                   flat=not irregular)
+                    new_data.append(coords)
                 for vd in data.vdims:
-                    gridded[vd.name] = data.dimension_values(vd, flat=False)
-                data = tuple(gridded.values())
+                    new_data.append(interface.values(data, vd, flat=False, compute=False))
+                data = tuple(new_data)
             else:
                 data = tuple(data.columns().values())
         elif isinstance(data, Element):

holoviews/operation/datashader.py

@@ -1020,7 +1020,48 @@ class quadmesh_rasterize(trimesh_rasterize):
     """
 
     def _precompute(self, element, agg):
-        return super(quadmesh_rasterize, self)._precompute(element.trimesh(), agg)
+        if ds_version <= '0.7.0':
+            return super(quadmesh_rasterize, self)._precompute(element.trimesh(), agg)
+
+    def _process(self, element, key=None):
+        if ds_version <= '0.7.0':
+            return super(quadmesh_rasterize, self)._process(element, key)
+
+        if element.interface.datatype != 'xarray':
+            element = element.clone(datatype=['xarray'])
+        data = element.data
+
+        x, y = element.kdims
+        agg_fn = self._get_aggregator(element)
+        info = self._get_sampling(element, x, y)
+        (x_range, y_range), (xs, ys), (width, height), (xtype, ytype) = info
+        if xtype == 'datetime':
+            data[x.name] = data[x.name].astype('datetime64[us]').astype('int64')
+        if ytype == 'datetime':
+            data[y.name] = data[y.name].astype('datetime64[us]').astype('int64')
+
+        # Compute bounds (converting datetimes)
+        ((x0, x1), (y0, y1)), (xs, ys) = self._dt_transform(
+            x_range, y_range, xs, ys, xtype, ytype
+        )
+        params = dict(get_param_values(element), datatype=['xarray'],
+                      bounds=(x0, y0, x1, y1))
+
+        if width == 0 or height == 0:
+            return self._empty_agg(element, x, y, width, height, xs, ys, agg_fn, **params)
+
+        cvs = ds.Canvas(plot_width=width, plot_height=height,
+                        x_range=x_range, y_range=y_range)
+
+        vdim = getattr(agg_fn, 'column', element.vdims[0].name)
+        agg = cvs.quadmesh(data[vdim], x.name, y.name, agg_fn)
+        xdim, ydim = list(agg.dims)[:2][::-1]
+        if xtype == "datetime":
+            agg[xdim] = (agg[xdim]/1e3).astype('datetime64[us]')
+        if ytype == "datetime":
+            agg[ydim] = (agg[ydim]/1e3).astype('datetime64[us]')
+
+        return Image(agg, **params)
 
 
 

holoviews/tests/operation/testdatashader.py

@@ -626,14 +626,14 @@ def test_rasterize_trimesh_string_aggregator(self):
     def test_rasterize_quadmesh(self):
         qmesh = QuadMesh(([0, 1], [0, 1], np.array([[0, 1], [2, 3]])))
         img = rasterize(qmesh, width=3, height=3, dynamic=False, aggregator=ds.mean('z'))
-        image = Image(np.array([[2., 3., np.NaN], [0, 1, np.NaN], [np.NaN, np.NaN, np.NaN]]),
+        image = Image(np.array([[2, 3, 3], [2, 3, 3], [0, 1, 1]]),
                       bounds=(-.5, -.5, 1.5, 1.5))
         self.assertEqual(img, image)
 
     def test_rasterize_quadmesh_string_aggregator(self):
         qmesh = QuadMesh(([0, 1], [0, 1], np.array([[0, 1], [2, 3]])))
         img = rasterize(qmesh, width=3, height=3, dynamic=False, aggregator='mean')
-        image = Image(np.array([[2., 3., np.NaN], [0, 1, np.NaN], [np.NaN, np.NaN, np.NaN]]),
+        image = Image(np.array([[2, 3, 3], [2, 3, 3], [0, 1, 1]]),
                       bounds=(-.5, -.5, 1.5, 1.5))
         self.assertEqual(img, image)