I got this error with a small example, so I thought I'd post it for you. I could only get it to work when split over two files. Main.hs: import qualified Data.Vector.Unboxed as U import Helper main = do let iters = 100 dim = 221184 y = U.replicate dim 0 :: U.Vector (ZqW M) let ans = iterate (f y) y !! iters putStr $ (show $ U.foldl1' (+) ans) Helper.hs {-# LANGUAGE FlexibleContexts, StandaloneDeriving, GeneralizedNewtypeDeriving, MultiParamTypeClasses #-} module VectorTestHelper (ZqW,f,M) where import qualified Data.Vector.Unboxed as U import qualified Data.Vector.Generic as V import Data.Vector.Generic.Mutable as M f :: (Num r, V.Vector v r) => v r -> v r -> v r {-# SPECIALIZE f :: (Num (ZqW m Int)) => U.Vector (ZqW m Int) -> U.Vector (ZqW m Int) -> U.Vector (ZqW m Int) #-} f x y = V.zipWith (+) x y newtype ZqW p i = T i deriving (U.Unbox, Show) deriving instance (U.Unbox i) => V.Vector U.Vector (ZqW p i) deriving instance (U.Unbox i) => MVector U.MVector (ZqW p i) class Foo a b data M instance Foo M Int instance (Foo p i, Integral i) => Num (ZqW p i) where (T a) + (T b) = T $ (a+b) fromInteger x = T $ fromInteger x It's possible I'm abusing SPECIALIZE here, but I'm trying to get Unboxed vector specialization, even though I have a phantom type. (In practice, the phantom will represent a modulus and will be used in the Num instance). When compiling with GHC 7.6.2 and -O2, I get a dozen or so "match_co: needs more cases" warnings. Indeed, based on the runtime, it appears that specialization is not happening. How to actually make this work is a whole different question... -- View this message in context: http://haskell.1045720.n5.nabble.com/match-co-needs-more-cases-tp5730855p573... Sent from the Haskell - Glasgow-haskell-users mailing list archive at Nabble.com.

specialize only fires on functions that have type class constraints / are part of a type class. Furthermore, the function needs to be marked INLINEABLE or INLINE for specialization to work (unless the specialize pragma was written in the defining module) not sure if that helps, cheers -Carter On Thu, Nov 7, 2013 at 7:17 PM, Evan Laforge wrote:

On Thu, Nov 7, 2013 at 11:11 AM, crockeea wrote:

...

I got this error with a small example, so I thought I'd post it for you. I could only get it to work when split over two files.

Mine is similar, sorry I've been lazy about getting a small reproduction, I assumed it wasn't too important.

I have a generic library that uses Data.Vector.Generic, along with a bunch of SPECIALIZE and INLINEABLE for a particular monomorphic Unboxed use. I don't know about the INLINEABLE, but the SPECIALIZE does wonders for performance, otherwise it doesn't notice that the operation can be unboxed.

So it's a bit worrisome to me if the SPECIALIZEs aren't firing. I did profiling before and they made my vector operations fall off of the expensive list, but that was before upgrading ghc and getting the new error msgs.

Would it be useful for me to boil down my example too, or is this one enough to work on? Mine is simpler in that it specializes to a monomorphic Storable.Vector Double. _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users