[Haskell] Speed of ByteString.Lazy
chad.scherrer at gmail.com
Thu Jun 29 14:43:02 EDT 2006
No. I suppose "man wc" would have helped, but this has been entertaining,
Times for lc and wc -l seem comparable over a couple of runs. So in any
case, it's encouraging that it's so easy to reach speeds comparable to
(presumably) highly-tuned C code like this.
On 6/29/06, Robby Findler <robby at cs.uchicago.edu> wrote:
> Just out of curiosity, did you try "wc -l"?
> On Jun 29, 2006, at 1:18 PM, Chad Scherrer wrote:
> > I have a bunch of data files where each line represents a data
> > point. It's nice to be able to quickly tell how many data points I
> > have. I had been using wc, like this:
> > % cat *.txt | /usr/bin/time wc
> > 2350570 4701140 49149973
> > 5.81user 0.03system 0:06.08elapsed 95%CPU (0avgtext+0avgdata
> > 0maxresident)k
> > 0inputs+0outputs (152major+18minor)pagefaults 0swaps
> > I only really care about the line count and the time it takes. For
> > larger data sets, I was getting tired of waiting for wc, and I
> > wondered whether ByteString.Lazy could help me do better. So I
> > wrote a 2-liner:
> > import qualified Data.ByteString.Lazy.Char8 as L
> > main = L.getContents >>= print . L.count '\n'
> > ... and compiled this as "lc". It doesn't get much simpler than
> > that. How does it perform?
> > % cat *.txt | /usr/bin/time lc
> > 2350570
> > 0.09user 0.13system 0:00.24elapsed 89%CPU (0avgtext+0avgdata
> > 0maxresident)k
> > 0inputs+0outputs (199major+211minor)pagefaults 0swaps
> > Wow. 64 times as fast for this run, with almost no effort on my
> > part. Granted, wc is doing more work, but the number of words and
> > characters aren't interesting to me in this case, anyway. I can't
> > imagine (implementation time)*(execution time) being much shorter.
> > Thanks, Don!
> > --
> > Chad Scherrer
> > "Time flies like an arrow; fruit flies like a banana" -- Groucho Marx
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"Time flies like an arrow; fruit flies like a banana" -- Groucho Marx
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