Salvatore Insalaco wrote:
Hi Andrew, just a profiling suggestion: did you try to use the SCC cost-centre annotations for profiling? If you want to know precisely what takes 60% of time, you can try: bn = {-# SCC "IntegerConversion" #-} 4 * fromIntegral wn b0 = {-# SCC "ByteStringIndexing" #-} B.index bi (bn+0) b1 = {-# SCC "ByteStringIndexing" #-} B.index bi (bn+1) b2 = {-# SCC "ByteStringIndexing" #-} B.index bi (bn+2) b3 = {-# SCC "ByteStringIndexing" #-} B.index bi (bn+3) w = foldl' (\w b -> shiftL w 8 .|. fromIntegral b) 0 [b3,b2,b1,b0] in {-# SCC "ArrayWriting" #-} unsafeWrite temp wn w
In profiling the time of all expressions with the same SCC "name" will be summed. You can get more information about SCC here: http://www.haskell.org/ghc/docs/latest/html/users_guide/profiling.html#cost-...
OK, I'll give that a try...
One advice: I've seen various md5sum implementations in C, all using about the same algorithms and data structures, and they performed even with 10x time differences between them; md5summing fast is not a really simple problem. If I were you I would drop the comparison with ultra-optimized C and concentrate on "does my high-level-good-looking-super-readable implementation perform acceptably?".
What "acceptably" means is left as an exercise to the reader.
Well, so long as it can hash 500 MB of data in a few minutes without using absurd amounts of RAM, that'll do for me. ;-) [I actually wanted to do this for a project at work. When I discovered that none of the available Haskell implementations are fast enough, I tried to write my own. But that wasn't fast enough either. So I ended up being forced to call md5sum.exe and attempt to parse its output. Obviously having a real Haskell function would be infinitely more portable and convinient...]