[QGIS-Developer] Processing plugin algorithm slows down in graphical modeler

[Clemens Raffler]

Thank you Nyall for your reply!

This gives me some more insights about how algorithm execution is 
implemented in models. I will try to test this issue with other 
processing algorithms (also other plugin algorithms). Maybe this gives 
some insight on whether it is a plugin or QGIS related issue.

Best,
Clemens


On 26.08.19 01:15, Nyall Dawson wrote:
> On Sun, 25 Aug 2019 at 00:39, Clemens Raffler <clemens.raffler at gmail.com> wrote:
>> Dear QGIS Devs,
>>
>> Recently, I received two messages from users concerning the speed of
>> processing algorithms which are implemented in the QNEAT3 plugin. More
>> specifically, they report that the execution time of algorithms slow
>> down up to 10 times when the algorithm is used in the graphical modeler
>> compared to manual execution from the processing toolbox (used
>> algorithm: OD Matrix from Layers as Lines (m:n)). I link the ticket from
>> the QNEAT3 repository here for reference:
>> https://github.com/root676/QNEAT3/issues/21
>>
>> I would like to identify the cause of this problem because on the first
>> look I can't relate it to any implementation flaws on the plugin side.
>> Has anyone else experienced this problem with other processing plugins
>> or core algorithms? I didn't have time yet to check if core algorithms
>> are affected too. Could it be some kind of bug related to the graphical
>> modeler? Do you have any hints what could cause this problem on the
>> plugin side so I can fix it? Tanks in advance!
> The only difference I can think of between running them in the toolbox
> vs models is that when you run a model it's always run in the main
> thread, including all the child algorithms inside that model. When you
> run direct from the toolbox then **some** algorithms are flagged as
> safe to run in background threads and won't be run on the main thread.
>
> So potentially they are seeing a slowdown due to this, and other stuff
> clogging up the main thread and slowing down the execution...
>
> Nyall