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/text<http://hackage.haskell.org/package/text> [2] http://hackage.haskell.org/**package/bytestring<http://hackage.haskell.org/package/bytestring>
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