#9646: Simplifer non-determinism leading to 8 fold difference in run time performance -------------------------------------+------------------------------------- Reporter: erikd | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Runtime | Difficulty: Unknown performance bug | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): I spent a few minutes earlier today, and indeed I'm sure that difference in eta expansion is the cause of the trouble. What I do not understand is why it happens. Would you be prepared to cut down the example still more? Dump the Criterion wrapping. Just leave enough to reproduce the strange difference in Core generated in the wot different ways. Strip away everything else; eg we don't actually need to run the program any more. Thanks Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9646#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler