[QGIS-Developer] Question

[Raymond Nijssen]

Hi Guillaume,

A 5% progress after 5 days still sounds extremely slow! That would take 
approximately 100 days to finish on 1 core, or 2 days (72 hours!) on 32 
cores.

I don't know how large or complicated these shapefiles are, but you 
might try to find the solution in another way.

- Make sure you are using indexes?
- Select non-overlapping shapes and delete them?
- Split the files in parts?
- Move to Postgis? (Am I allowed to suggest that here? ;) )

@Marco Shouldn't that code end up in QGIS or is it still in your repo 
for a reason?

Kind regards,
Raymond




On 22-10-2020 07:20, Marco Hugentobler wrote:
> Hi Guillaume
> 
> 
>  >My question: Is there a way to take advantage of the fact that I have 
> 32 cores on my computer with QGIS to make this calculation? I don't 
> understand why it is so slow.
> 
> 
> Yes, there is. Compile the code from the 
> 'processing_multithreaded_vector' branch in my repo 
> (https://github.com/mhugent/QGIS/tree/processing_multithreaded_vector). 
> It calculates the difference operation on multiple cores (see also 
> https://github.com/qgis/QGIS/pull/33365).
> 
> 
> Regards,
> 
> Marco
> 
> 
> Am 22.10.20 um 03:05 schrieb guillaume martel:
>> Hi,
>>
>> I don't know if I'm writing at the wrong place...
>>
>> I have 2 shapefiles and I want to do a "difference operation" 
>> (https://docs.qgis.org/3.10/en/docs/user_manual/processing_algs/qgis/vectoroverlay.html).
>>
>> My issue is as follow: Even though I have a powerful computer, after 5 
>> days the calculation is only at 5%.
>>
>> My question: Is there a way to take advantage of the fact that I have 
>> 32 cores on my computer with QGIS to make this calculation? I don't 
>> understand why it is so slow.
>>
>> Thank you for your help.
>>
>> Guillaume
>>
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> 
> -- 
> Dr. Marco Hugentobler
> Sourcepole -  Linux & Open Source Solutions
> Weberstrasse 5, CH-8004 Zürich, Switzerland
> marco.hugentobler at sourcepole.ch  http://www.sourcepole.ch
> 
> 
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