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. [1] http://hackage.haskell.org/package/text [2] http://hackage.haskell.org/package/bytestring