[gdal-dev] four threads are huh, five are buh? Regressions w/ GDAL 3.5.2/PROJ_9.1.0

[Even Rouault]

Christian,

I suspect the issue is not that much jumping from 4 to 5 threads, but 
some latent issue in your code or in GDAL/PROJ that becomes more 
visible. First thing to check: are you sure you are not using a given 
GDAL / OGR object simultaneously in more than one thread ?

If that's not the issue, if you want effective help, I'm afraid you'll 
have to go through the effort of writing a minimal standalone reproducer 
(code+data) that you can share with us.

Even

Le 11/10/2022 à 14:56, Christian Brock via gdal-dev a écrit :
> I have some special issue and would be glad for suggestions.
>
> We run complex regression tests using environmental files -- too complex for a bug report ;-(
>
> Moving from GDAL_2.4.2/PROJ_5.2.0 to GDAL 3.5.2/PROJ_9.1.0 we run into regressions.
>
> The most stunning observation is that the issue only occurs when USING MORE THAN FOUR THREADS!
> Can anyone think of something that is true with five or more threads but not below?
>
> Besides this I should mention, that we use Java bindings
>
> The issue is
> - file format independent,
> - were observed on ubuntu 20.04 and 22.04,
> - affects a sample with the following coordinate system:
> PROJCS["Transverse Mercator",GEOGCS["Potsdam_IST_V2_0",DATUM["Potsdam_IST_V2_0",SPHEROID["Bessel",6377397.155,299.152813106079],TOWGS84[583,68,399.5,0,0,1.36E-05,1.13E-05]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",9],PARAMETER["scale_factor",1],PARAMETER["false_easting",3500000],PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["Easting",EAST],AXIS["Northing",NORTH]]"
> - WGS84 and all UTM systems are good.
>
> I should also mention, that this issue affects only the second sample, when I run more than one sample with the PROJCS above.
> When I change the sample order, it is the second sample again!
>
> And as a final point, there are random memory corruptions every couple of hours.
>
> So again, please step forward when you know of anything inside GDAL, PROJ or Java bindings that cares about the number of threads.
>
> Many thanks
> --Chr.
>
>
>
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