enthought/distarray — pull request #376 by kwmsmith (2014-05-19 19:40:22+00:00)
Title: Allow Distribution and DistArrays on subset of targets

This PR adds a `targets` attribute to `Distribution` objects, allowing Distributions and DistArrays to exist on a subset of targets. All communication methods are updated to reflect the change.

On the local side, it is necessary to create a sub-communicator for each grouping of sub-targets. These sub-communicators are cached in the client-side context object to reduce overall communication.

Sub-target support is a necessary prerequisite for reduction methods and for certain slicing operations.