[Haskell-cafe] performance difference for binary-0.4.3.1 with ghc-6.8.3 and ghc-6.10

[John Lato]

Hello,

I was experimenting with using ghc-6.10.0.20081007 on a project, and
it seems that binary-0.4.3.1 has markedly worse performance in certain
cases.  With the following simple test:

> import qualified Data.ByteString.Lazy as L
> import Data.Binary
> import Data.Binary.Get
> import Control.Monad
>
> main :: IO ()
> main = do
>     b <- L.readFile "some_binary_file"
>     putStrLn $ show $ runGet getter b

> getter :: Get [Word16]
> getter = replicateM 1000000 getWord16le

running this program compiled with ghc-6.10 takes about 4 times as
long (and consumes much more memory) as when compiled with ghc-6.8.3.
The extra time appears to be proportional to the number of elements
processed in the Get.  Running the programs with -hT shows a clear
memory difference, which I think is the source of the problem.  I've
placed pdfs of that output at https://webspace.utexas.edu/latojw/data/

The difference seems to manifest itself only when the elements are
actually processed; changing "show $ runGet " to "show $ length $
runGet " is slightly faster in 6.10.

I was working on an Intel Mac with OS 10.4, binary-0.4.3.1, and
bytestring-0.9.1.4.  Can anyone confirm this, or suggest what might be
the difference?

Thank you,
John Lato