#8763: forM_ [1..N] does not get fused (10 times slower than go function) -------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.6.3 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 nh2): Replying to [comment:30 simonpj]:
Real programs usually depend on input data. So this probem may be less of a probem in practice than in benchmarks.
Just wanted to chime in that I found this problem in a real-world program, where I looped over all 32-bit integers. Similarly, these known-at- compile-time iteration lists may appear in inner loops of algorithms or data structures (like B-trees with fixed B, or image convolution kernels with fixed size, e.g. 3x3 image templates). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8763#comment:31 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler