ndmitchell:
Hi,
In an application I'm writing with Data.Binary I'm seeing very fast write performance (instant), but much slower read performance. Can you advise where I might be going wrong?
Can you try binary 0.5 , just released 20 mins ago? There was definitely some slow downs due to inlining that I've mostly fixed in this release.
The data type I'm serialising is roughly: Map String [Either (String,[String]) [(String,Int)]]
A lot of the String's are likely to be identical, and the end file size is 1Mb. Time taken with ghc -O2 is 0.4 seconds.
Map serialisation was sub-optimal. That's been improved today's release.
Various questions/thoughts I've had:
1) Is reading a lot slower than writing by necessity?
Nope. Shouldn't be.
2) The storage for String seems to be raw strings, which is nice. Would I get a substantial speedup by moving to bytestrings instead of strings? If I hashed the strings and stored common ones in a hash table is it likely to be a big win?
Yep and maybe.
3) How long might you expect 1Mb to take to read?
Thanks for the library, its miles faster than the Read/Show I was using before - but I'm still hoping that reading 1Mb of data can be instant :-)
Tiny fractions of a second. $ cat A.hs import qualified Data.ByteString as B import System.Environment main = do [f] <- getArgs print . B.length =<< B.readFile f $ du -hs /usr/share/dict/cracklib-small 472K /usr/share/dict/cracklib-small $ time ./A /usr/share/dict/cracklib-small 477023 ./A /usr/share/dict/cracklib-small 0.00s user 0.01s system 122% cpu 0.005 total If you're not seeing results like that, with binary 0.5, let's look deeper. -- Don