kamil: > Hi all, > > I want to learn how to optimize Haskell code on the Norvig's spelling > correction program [1]. Peter Norvig has written the program in > Python, > quite a literate translation to Haskell (thanks to Grzegorz Chrupala) > [2] was also available. > > Both versions are about 23 LOCs, and Haskell version is four times > slower, 2m25s versus 36s. All the numbers I give come from running the > program on a list of 806 misspellings, Haskell version compiled with - > O2 > and -fforce-recomp flags. > > I started with trial and error approach. Just preventing a repetitive > call to keysSet brought the running time down to 1m48s. I also > restructured the edits1 function and dropped all uses of sets, which > haven't been pulling their own weight. This brought the running time > down to 55s. Not quite there yet but close. > > Reading the Profiling chapter in the RWH book enabled me to do some > more > informed optimizing. At this point the GC time was about 2% of the > overall runnig time, Grzegorz has done a good job of using strict > versions of functions where necessary. The timing per expression > however > showed something useful, 70% of the time was being spent around > determining membership in the known words dictionary (Data.Map). There > are about 30 000 items in the dictionary.
What are the keys in your Map? Strict ByteStrings? And you're using ghc 6.10.x? -- Don _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
