Fixed dtype handling in _slicing_distributor's bincount.

d2o/distributed_data_object.py

@@ -1424,8 +1424,9 @@ class distributed_data_object(object):
 
         Returns
         -------
-        out : numpy.ndarray of ints
-            The result of binning `self`.
+        out : numpy.ndarray
+            The result of binning `self`. The returned dtype is `int` if
+            no weights were given, and `np.float` otherwise.
 
         Raises
         ------
@@ -1515,7 +1516,7 @@ class distributed_data_object(object):
                  hermitian=False, copy=True, **kwargs):
         """ Takes the supplied `data` and distributes it to the nodes.
 
-        Essentially this method behaves like `d2o[to_key] = data[from_key]`.
+        Essentially this method behaves like `d2o[to_key] = data[from_key]`
         In order to makes this process efficient, the built-in distributors
         do not evaluate the object `d2o[from_key]` explicitly. Instead, the
         individual nodes check for the self-affecting part of `to_key`, then

d2o/distributor_factory.py

@@ -1489,10 +1489,17 @@ class _slicing_distributor(distributor):
         return global_unique_data
 
     def bincount(self, local_data, local_weights, minlength):
+        if local_weights is None:
+            result_dtype = np.int
+        else:
+            result_dtype = np.float
+
         local_counts = np.bincount(local_data,
                                    weights=local_weights,
                                    minlength=minlength)
 
+        # cast the local_counts to the right dtype while avoiding copying
+        local_counts = np.array(local_counts, copy=False, dtype=result_dtype)
         global_counts = np.empty_like(local_counts)
         self._Allreduce_helper(local_counts,
                                global_counts,