Implementing __hash__ and __eq__ for BatchedSend

[jakirkham]

In Scheduler.report we collect a set of comms for the Clients. Looking more closely at the contents of self.client_comms, it appears to just contain BatchedSend objects. Putting these objects in a set will wind up using __eq__ and __hash__. Neither of these appear to be defined by BatchedSend. As a result a good chunk of time is spent hashing these objects by some fallback mechanism before adding them to the set in Scheduler.report. Would be good to have implementations of __eq__ and __hash__ for BatchedSend to avoid this issue.

[jakirkham]

Alternatively we might investigate another way to write this code so it doesn't rely on hashing and comparing BatchedSend objects.

[jakirkham]

Maybe another way to look at this is, when would a BatchedSend object be used for more than 1 Client?

cc @mrocklin (in case you have thoughts here 😉)

[mrocklin]

It seems reasonable that there would be only one BatchedSend per Client. In this situation I would try implementing this (hopefully it's cheap to do), and then seeing if any tests fail. If no tests fail then we're good to go.

[mrocklin]

We can also ask @jrbourbeau to do this if y'all are less familiar here. James is fairly adept at these sorts of changes.

[jakirkham]

Found a good way to do this with a dict ( #4275 ), which should get us past this issue. It may be possible to simplify this further to a list, but that might not matter much.