[gdal-dev] gdalwarp and gdaladdo in multi-threaded mode

[Even Rouault]

Le jeudi 25 février 2016 14:26:03, Neumann, Andreas a écrit :
> Hi,
> 
> I noticed that in GDAL >2.0 some utilities and operations support
> multi-threaded calculations, such as the gdalwarp utility. I tested it
> and it seems to work well. I can see that multiple CPU cores are busy.
> 
> Question 1: in gdalwarp there are at least two ways to tell that it
> should use more than one CPU:
> 
> -multi

This parallelizes I/O and CPU operations. 

> 
> and
> 
> -wo NUM_THREADS=ALL_CPUS or a nr of cores

This parallelizes CPU operations over several cores.

> 
> Are these two flags redudant? Is either one enough or should I specify
> both?

Both are independant and can be combined.

> 
> Question 2: can I also speed up the gdaladdo utility?

Not as directly as above, but increasing GDAL_CACHEMAX may help for big 
rasters.

> 
> Thank you for your replies!
> 
> Andreas

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