[gdal-dev] More info on gdalwarp resampling methods?

[Even Rouault]

Matt,

I see that in the -multi mode, the I/O threads waits for a maximum of 10 
minutes for the computation thread to have finished. And you likely hit 
that limit because of the large value of -wm you set. There's no reason 
we max at 10 minutes however. Please find a but about that, including my 
analysis.

For better speed, I'd suggest you add --config GDAL_NUM_THREADS ALL_CPUS 
(or a given number of threads). The -multi switch only does one thread 
for I/O and one thread for computation. By adding --config 
GDAL_NUM_THREADS xxx you'll also multi-thread the computation part. The 
gain of -multi alone is generally neglectable. We should probably make 
-multi turn on --config GDAL_NUM_THREADS ALL_CPUS as well.

I also see that the mode resampling spend an awful lot of time on line 
"memset(panVals, 0, nBins*sizeof(int));" where nBins=65536 on Int16 
data, and that for each output pixel. We could probably do something 
much less expensive for most cases. Please file a separate enhancement 
ticket about that particular case.

Even


Le 31/03/2021 à 18:46, Matt.Wilkie at yukon.ca a écrit :
> gdalwarp --config GDAL_CACHEMAX 4096 -wm 512 -multi -co TILED=YES -co 
> COMPRESS=ZSTD -t_srs EPSG:3579 -r mode -co predictor=2 
> tri_mergedDEM_clipped_16bit.tif 
> tri_mergedDEM_clipped_16bit_ytalb-rs-mode.tif 

-- 
http://www.spatialys.com
My software is free, but my time generally not.

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