#14208: Performance with O0 is much better than the default or with -O2, runghc performs the best -------------------------------------+------------------------------------- Reporter: harendra | Owner: osa1 Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by harendra): @mpickering is there something to read about how things do and don't get optimized with CPS especially with GHC? What are the pitfalls and why it does not optimize well? I am very much interested in this, any pointers will be appreciated. I was using the direct style before and I had some trouble with it, I had to use a lot of SPECIALIZE to IO types to extract decent performance wherever I was using monad polymorphic instances. The performance did not seem to be much better compared to CPS. Maybe I am wrongly attributing the problem to CPS-vs-Direct style and it might have been something stupid that I did, at that time. But I never had any similar problem in CPS style and then I never went back to direct. Though I want to try and see if direct would be any better but it will take some time and effort to do that. However, there is some proof that direct style is not very much different in that the "streaming" library performance is more or less the same as this library and "streaming" is actually more or less the same thing but written in direct style. See the performance comparison between "streaming" and "streamly" here: https://github.com/composewell/streaming- benchmarks/blob/master/charts-1/CheaperOperations.svg -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14208#comment:37 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler