Paul Sandoz paul.sandoz at
Wed Oct 3 09:27:23 PDT 2012


Here is an implementation of GroupByOp.evaluateParallel:

based from the previous patches in my queue.

The casts from Map<K, StreamBuilder<T>> to Map<K, Collection<T>> are annoying. Perhaps we need a more formal transition from StreamBuilder to Collection?

The reduction phase (traversing up the computation tree) could be more efficient if two or more StreamBuilder<T> instances could be efficiently merged, perhaps if we know something about the implementation data structures. This feels very like what TreeUtils.Node does.

Potentially there could be another parallel evaluation if we wanted to "flatten" the tree of values to T[].

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