[Haskell-cafe] performance difference for binary-0.4.3.1 with
ghc-6.8.3 and ghc-6.10
jwlato at gmail.com
Wed Oct 29 05:30:44 EDT 2008
On Tue, Oct 28, 2008 at 5:43 PM, Don Stewart <dons at galois.com> wrote:
>> I was experimenting with using ghc-126.96.36.19981007 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.
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