Michael Walker c4eefd4849 Avoid decisions which will immediately block. ... If a decision will immediately block without changing the global state, then there is no point in making it: no state will become reachable from it which isn't reachable through some other option we have available. This has three parts: - When the prefix runs out and the scheduler is making decisions, it filters out decisions which will immediately block. - When a subtree is being added, it records which decisions will immediately block. - When backtracking points are being added, it filters out ones in this block list. This optimisation is likely to only be useful when threads are communicating a lot. For instance, a `parMap id` is totally unaffected by this, but the test cases drop from an average of 64 runs to 42.		2015-07-20 16:16:46 +01:00
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Internal.hs	Avoid decisions which will immediately block.	2015-07-20 16:16:46 +01:00