Thanks that is *exactly* the problem I am having. The missing line breaks are kind of weird. I will try the newest head (which will mean getting about 20 libs to compile...) and report back. I left the core out intentionally because the vector library tends to produce ugly core when it can not optimize. Should the problem *not* go away with HEAD (right now I am using 6.12.3) then I will create a self-contained set of files that reproduce the problem. Thanks again, Christian ----- Original message -----
It's hard to read your code because the line breaks have been removed. Moreover I think your code depends on some unspecified Hackage package. And I couldn't find the enclosed Core dumps. Nor do you specify which version of GHC you are using.
Still I believe that the nub is this. You have a class with a default method declaration
class FoldFunctions a where opt = <blah>
and you get different behaviour if you say
instance FoldFunctions Int from instance FoldFunctions Int where opt = <blah>
That's surprising because the second case simply fills in the method with the identical code to the code in the class declaration.
Is that right?
If so, I think you might want to try the HEAD. Can you do that (use a binary snapshot). I think I fixed this default-method-inlining stuff so that there is no difference between the above two.
But I could have failed, or there could be something else going on in your example.
Simon
| -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell- | users-bounces@haskell.org] On Behalf Of Christian Höner zu Siederdissen | Sent: 26 August 2010 10:36 | To: Glasgow-Haskell-Users | Subject: late optimization of typeclass callers | | Hi, | | I do have the problem that my code is not completely optimized. We begin with | | -- Ring.hs | class Ring a where | rmult :: a -> a -> a | zero :: a | | -- PrimitiveArray.hs | class PrimArrayOps a b where | data PrimArray a b :: * | unsafeIndex :: PrimArray a b -> a -> b | | -- PAInstances.hs | -- for any 'a' of Data.Primitive.Types by Roman, have unboxed arrays instance | (Prim a) => PrimArrayOps where | data PrimArray (Int,Int) a = PaIIxI {-# UNPACK #-} !(Int,Int) {-# UNPACK #- | } !ByteArray | unsafeIndex (PaIIxI (mI,mJ) arr) (i,j) = {-# CORE "IIxIunsafeIndex" #-} | case (i*(mJ+1)+j) of idx -> indexByteArray arr idx | | -- RNAfoldFunctions.hs | -- VU.Unbox a, because of the vector package import Data.Vector.Unboxed as VU | class (Ring a, VU.Unbox a, Prim a) => FoldFunctions a where | opt = VU.foldl' rmult zero $ base turnertables inp table table i j | | base trnr inp m m1 i j = VU.zipWith rmult ms m1s where | cnt = j-i-2 -- TODO when to stop? | ms = VU.map (\ik -> m `unsafeIndex` ik) $ VU.generate cnt (\k -> | (i,i+k)) | m1s = VU.map (\kj -> m1 `unsafeIndex` kj) $ VU.generate cnt (\k -> | (k+1+i,j)) {-# INLINE multibranchCloseBase #-} | | | | If I now use this stuff... | -- [1] | instance Ring Int where | rmult = min | zero = 10000 | instance FoldFunctions Int | module MyProgram where | main = do | let val = opt trnr inp myM myM1 15 78 | | I get this core [1]. If I do this | -- [2] | instance Ring Int where | rmult = min | zero = 10000 | instance FoldFunctions Int | opt = VU.foldl' rmult zero $ base turnertables inp table table i j module | MyProgram where main = do | let myM = PrimArray of (Int,Int) with Int values | ... | let val = opt trnr inp myM myM1 15 78 | | Is there a way to get the program without an explicit FoldFunctions instance | to specialize to the same Core as the second? The runtime (Criterion was | used) is 7.1us (or worse) for [1] and 2.7us for [2]. I could put nice INLINEs | everywhere but they do not help optimizing. These functions run O(n^2) times, | with n between 100 and 10000. The core shows that temporary arrays are even | created, filled, and then the fold run over them. | | So basically, can I get code running through several class instances to be | optimized at the caller, where all instances are known? Otherwise I could | live with [2], but as the code will almost always be the same for | FoldFunctions instances, it would be really nice to be able to use the | defaults that were defined on (Ring a, VU.Unbox a, Prim a). | | Thanks, | Christian