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

[John Lato]

On Tue, Oct 28, 2008 at 5:43 PM, Don Stewart <dons at galois.com> wrote:
> jwlato:
>> 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?
>>
>
> Is this the sole test case?
>
> I can investigate. Though perhaps using a newer GHC release candidate is
> also a good idea.
>
> -- Don
>

I'll try a newer release candidate, although at the time I first ran
this it was the latest.

Last night I tried creating the bytestring using "repeat 1" to remove
the file I/O, and the result was the same.  There are a few other
things I want to try as well (removing replicateM, folding the list to
force values rather than printing them all), but my time is extremely
limited at the moment.

John