[Qgis-developer] Parallel Development

[Matthias Kuhn]

Hi Benjamin,

Thank you for your interest in the project.
I was looking at a problem today and thought of your mail to the list.
In case you still would like to contribute to QGIS with a task 
concerning parallelisation, I would have a place, where I can imagine a 
true benefit of this.
QGIS makes use of the PAL library, which allows for automated placement 
of labels [1] using collision detection. To my knowledge (pardon me if 
I'm wrong), this library is not widely used outside of QGIS. 
Unfortunately it can be really time consuming, as it compares each 
possible label position to each other. I think that this job could 
greatly profit from being split between different cores.
While I'm not the author of this library, my understanding is that the 
loop on line 579 in pal.cpp [2] could be a place to start. If this loop 
could be split up into chunks being worked on by different threads, 
overall performance would benefit.
As far as I can see, there is quite a bit of code, that requires being 
checked for concurrency. I think it is feasible to solve these, but I 
can't tell what the real extent of this is.
Any help in this direction will surely be highly appreciated by the project.

Kind regards,
Matthias

[1]: http://pal.heig-vd.ch/ <http://pal.heig-vd.ch/>
[2]: 
https://github.com/qgis/Quantum-GIS/blob/master/src/core/pal/pal.cpp#L579



On 02/14/2013 04:30 PM, Benjamin Adcock wrote:
> Hi all,
>
> I am a graduate student looking to contribute to QGIS.  Specifically, 
> I am looking to tackle a project that requires parallel computing 
> techniques.
>
> I'm somewhat new here; from reading the archives it looks like there 
> is multithreading support in QGIS, maybe some support for OpenCL, but 
> it doesn't look like much has been done with it.
>
> Frankly, I don't know where to start.  If someone could point me in 
> the right direction, or if they have any insight into parts of the 
> codebase that could benefit from parallelization, I'd appreciate it.
>
> Ben Adcock
>
>
>
>
>
>
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