Andrew, I spent a reasonable amount of time making pureMD5 (available on hackage) faster, which mainly ment strictness annoitations and unboxing strict fields, but I also spent a good deal of time with the profiler. One of my early versions was fairly slow due to the converting of the LPS to blocks (an Isabelle proven 'blocks' function) caused O(n) space requirement. I've been meaning to revisit this to optimize more and look closly at GHC core. I'm on vacation now, but when I get back I'll try to make time to look at your code (unless its moot by then). Finally, I encourage anyone interested to make reasonably fast bytestring implementations of SHA algorithms as well - Haskell/Hackage has a number of pure and FFI implementations of MD5 but is a bit lacking in any other cryptographic algorithm. TomMD On Sat, 2008-05-17 at 15:51 +0100, Andrew Coppin wrote:
Hi folks.
OK, try this:
darcs get http://darcs.orphi.me.uk/MyMD5 cd MyMD5 ghc -O2 --make md5sum md5sum <some large filename>
On my PC, it takes 3.5 seconds to compute the MD5 hash of a 10 MB file. For comparison, the md5.exe I downloaded from the Internet does it instantaneously. It's literally so fast I can't even time it. As far as I know, my program always produces the *correct* answer, it just takes far too long to do it.
If anybody has any interesting insights as to why my version is so damned slow, I'd like to hear them. (Indeed, a description of the process for tracking the problem down would also be useful!)
[Much to my bemusement, when I had a look at the code, I discovered that tucked away in a corner somewhere, it reads a ByteString from disk and instantly converts it to [Word8]. Uh... oops? Anyway, eliminating this changed the numbers I get from the profiler, but it's still far too slow.]
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