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

[Alexander Dunlap]

On Sun, Oct 26, 2008 at 9:36 AM, John Lato <jwlato at gmail.com> wrote:
> 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
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With GHC 6.8.2:

test: too few bytes. Failed reading at byte position 1613914

real	0m27.573s
user	0m12.917s
sys	0m0.087s

With GHC 6.11.20081003:

test: too few bytes. Failed reading at byte position 1613914

real	0m21.528s
user	0m14.759s
sys	0m0.135s

I'm not using the exact same versions as you are, but I seem to be
getting different results.