On Fri, Feb 8, 2013 at 1:23 PM, Aleksey Khudyakov 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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