I've been playing with your example to optimize it a bit, I have to run but
here's what I have so far. It's about as fast as the Python code, I'll make
it faster when I have more time over the next few days.
See https://gist.github.com/etrepum/4747507 and
https://gist.github.com/etrepum/4747507/revisions
On Sat, Feb 9, 2013 at 2:35 PM, Nicolas Bock
On Fri, Feb 8, 2013 at 1:23 PM, Aleksey Khudyakov < alexey.skladnoy@gmail.com> wrote:
On 08.02.2013 23:26, Nicolas Bock wrote:
Hi list,
I wrote a script that reads matrix elements from standard input, parses the input using a regular expression, and then bins the matrix elements by magnitude. I wrote the same script in python (just to be sure :) ) and find that the python version vastly outperforms the Haskell script.
General performance hints
1) Strings are slow. Fast alternatives are text[1] for textual data and bytestrings[2] for binary data. I can't say anything about performance of Text.Regex.Posix.
2) Appending list wrong operation to do in performance sensitive code. (++) traverses its first argument so it's O(n) in its length.
What exactly are you tryeing to do? Create a histogram?
The Haskell script was compiled with "ghc --make printMatrixDecay.hs".
If you want performance you absolutely should use -O2.
Another question: When I compile the code with --make and -O2, and then run it on a larger matrix, I get this error message:
$ ./createMatrixDump.py -N 512 | ./printMatrixDecay Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it.
When I use "runghc" instead, I don't get an error. What does this error mean, and how do I fix it?
Thanks,
nick
[1] http://hackage.haskell.org/**package/texthttp://hackage.haskell.org/package/text [2] http://hackage.haskell.org/**package/bytestringhttp://hackage.haskell.org/package/bytestring
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