Re: profiler and/or debugger, loops vs vectorization

[David Bateman]

David Grohmann wrote:

> David Bateman wrote:
>
>>David Grohmann wrote:
>>  
>>
>>>So I have some code that runs in matlab (on a P3 500 mhz 512 MB ram 
>>>windows box) about 133 times faster (33 minutes to complete something 
>>>instead of 15 seconds)  than it does in octave( on a 4 processor 3.6 ghz 
>>>xeon machine with an ungodly amount of ram linux box). my guess is that 
>>>it is the use of loops and not vectorization.
>>>
>>>Is such a large performance hit likely caused by loops vs vectorization 
>>>or might there be another explanation besides that?
>>>
>>>I've searched online and haven't found anything to profile m files with, 
>>>other than in matlab. I have profiled it in matlab and sure enough it 
>>>does run the lines in the loops many (hundreds of thousands of times) 
>>>times but only one of the loops actually takes up a lot of run time. 
>>>This would probably be a good candidate for vectorizing. I suspect.
>>>
>>>So is there anything out there for profiling or stepping through code in 
>>>an m file in octave?
>>>
>>>I know I haven't posted the offending code, that is because I currently 
>>>don't have the authorization to do that. So my general question is how 
>>>do people profile their code and what not. I'm not asking you to fix my 
>>>code for me.
>>>
>>>Thank you for any help you provide,
>>>
>>>    
>>>
>>
>>My guess is that you are running a cygwin binary version of octave.
>>There is a major bug in the setjmp/longjmp exception handler of g++ for
>>versions later than 3.2 that causes major pain to octave. As far as I
>>know this bug in cygwin as not yet been addressed. The result is
>>sssllloooowwww code..
>>
>>D.
>>  
>>
> Octave was on a linux machine, matlab was on a windows machine.
>
> However it seems that vectorizing the code makes up the difference. I
> didn't know that such a performance boost would happen with vectorization.
>
The setjmp/longjmp issue is felt most in loops on cygwin..

D.

-- 
David Bateman                                address@hidden
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