#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 erikd): The repo at https://github.com/erikd/ghc-perfbug-test has been stripped back as far as possible and no longer needs either criterion or hspec. The code has been tested with ghc-7.8.3 and ghc-7.9.20140929 and both display the same problem. Cloning the repo, cd-ing into it and running `make` will build the code and then print out: {{{ Fast version etas : 0 Slow version etas : 18 }}} which is simply the count of the occurence of the identifier `eta` in the twp -ddump-simpl outputs generated from the same file. When this bug is fixed, both values should be zero. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9646#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler