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Re: [Haskell-cafe] Is Haskell capable of matching C in string processin

Subject: Re: [Haskell-cafe] Is Haskell capable of matching C in string processing performance?
From: Eugene Kirpichov
Date: Sat, 23 Jan 2010 11:55:40 +0300
Ironically, there's a TODO comment about that in the source of
Data.ByteString.Lazy, just below 'copy':

http://hackage.haskell.org/packages/archive/bytestring/0.9.0.4/doc/html/src/Data-ByteString-Lazy.html#copy

-- TODO defrag func that concatenates block together that are below a threshold
-- defrag :: ByteString -> ByteString

2010/1/23 Gregory Crosswhite <[email protected]>:
> I would say that counts as cheating because it assumes that knowledge of the 
> input in advance.  However, I wonder how it would perform if there were a 
> "reChunk" function that lazily built a new lazy ByteString by merging smaller 
> chunks together --- i.e., it would keep pullings chunks from the ByteString 
> until it reached some threshold size, merge them into a single strict 
> ByteString chunk, and then recursively continue processing the rest of the 
> lazy ByteString in this manner.
>
> Cheers,
> Greg
>
>
> On Jan 22, 2010, at 7:30 AM, Tom Nielsen wrote:
>
>>> It seems to me this indicates that the big expense here is the call into 
>>> the I/O system.
>>
>> So let's make fewer I/O calls:
>>
>> import Control.Monad
>> import qualified Data.ByteString.Char8 as S
>> import System.IO
>>
>> null_str1 = S.concat $ take 1000 $ repeat $ S.pack "null"
>>
>> n1 = 5000000 `div` 1000
>>
>> main = withBinaryFile "out3.json" WriteMode $ \h -> do
>> hPutStr h "["
>> replicateM_ n1 (S.hPutStr h null_str1)
>> hPutStr h "]"
>> ---
>> this is 10x faster. Whether this is cheating or not depends on what
>> John actually wants to do.
>>
>> Tom
>
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-- 
Eugene Kirpichov
Web IR developer, market.yandex.ru
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