[Haskell-cafe] performance question

[Bob Ippolito]

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 <nicolasbock at gmail.com> wrote:

>
>
>
> On Fri, Feb 8, 2013 at 1:23 PM, Aleksey Khudyakov <
> alexey.skladnoy at 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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>
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