#13001: EnumFromThenTo is is not a good producer -------------------------------------+------------------------------------- Reporter: George | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: MacOS X | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by akio):
since GHC doesn't know c is strict, it'll allocate a thunk for the second argument.
This is true. I was actually referring to another source of allocation: since the call to `c` is under-saturated, evaluating this call involves allocating a closure for the partial-application of `c`. This is also the case when the final consumer is `foldl'` instead of `length`. I think this is a general argument for marking *all* `FB` functions `INLINE [0]`. If `p = build pFB` is advertised as a good producer, a user would expect `foldl' f z p` to allocate no intermediate data structure. However, if `pFB` is not inlined, this expression will necessarily allocate a few closures for each eliminated cons cell. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13001#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler