[gdal-dev] GDAL using Nvidia - won't use OpenCL

[Even Rouault]

Le jeudi 18 février 2016 16:10:34, Jonathan Williams a écrit :
> OK, I've solved this one, too, but it took a bit more hunting and
> inserting of debug messages...
> 
> The issue in this case was the data.  I was using weather data in .grib2
> files, which comes in Float64 format. Digging into the
> gdalwarpkernel.cpp code, I see it is explicitly designed to only use up
> to Float32 with OpenCL. After running the file through GDAL_Translate
> first, it now makes use of OpenCL.

You don't necessarily have to gdal_translate. You could use the -wt Float32 
option of gdalwarp to select the working data type.

> 
> By any chance, does anyone know whether current GPU's, with current
> OpenCL code, can handle double-precision floating point?  I thought that
> was the case.
> 
> Anyway, OpenCL problem solved, and with the expected significant speedup.
> 
> Best,
> Jonathan
> 
> On 2/15/2016 1:40 PM, Jonathan Williams wrote:
> > Hello,
> > I've been trying to compile GDAL with OpenCL support for an Nvidia
> > gt555m (this is an Alienware m14x r1 laptop) on Ubuntu desktop (I wanted
> > to run it headless, but Ubuntu server failed to boot with the Nvidia
> > drivers and without X installed).
> > 
> > Per the instructions at various sites, including here:
> > https://wiki.tiker.net/OpenCLHowTo , I installed Ubuntu packages
> > nvidia-346, nvidia-346-uvm, nvidia-libopencl1-346 and
> > nvidia-opencl-icd-346. Other combinations seemed to fail, including
> > adding nvidia-opencl-dev, and more recent Ubuntu Nvidia driver versions
> > didn't include the uvm package (I think the current driver is the 361
> > series).
> > 
> > So, after installing these packages and making sure everything was in
> > order in /etc/OpenCL/vendors, I verified OpenCL was functional using
> > test packages like MandelGPU/MandelCPU. The OpenCL speedup was obvious
> > using these tests.
> > 
> > After a lot of trial-and-error compilations, this is my configuration
> > for GDAL with OpenCL:
> > 
> > ./configure \
> > --prefix=/usr \
> > --disable-rpath \
> > --with-threads=yes \
> > --with-ogr \
> > --with-geos \
> > --without-libtool \
> > --with-libz=internal \
> > --with-libtiff=internal \
> > --with-geotiff=internal \
> > --with-pg=/usr/bin/pg_config \
> > --with-expat-lib=/usr/lib/x86_64-linux-gnu/libexpat.so \
> > --with-netcdf=/usr/lib \
> > --with-png=internal \
> > --with-jpeg=internal \
> > --with-gif=internal \
> > --without-kakadu \
> > --without-mrsid \
> > --without-jp2mrsid \
> > --with-liblzma=yes \
> > --with-curl=/usr/lib/x86_64-linux-gnu \
> > --with-ecw=/usr/local/hexagon \
> > --with-python=yes \
> > --with-hide-internal-symbols \
> > --with-jasper=/usr/local \
> > --with-openjpeg=/usr/local \
> > --with-opencl=yes \
> > --with-opencl-include=/usr/include \
> > --with-opencl-lib="-L/usr/lib/x86_64-linux-gnu -lOpenCL"
> > 
> > While I did get a couple of errors with this, they seem unrelated to
> > anything important (complaining of a zero-length gnu_printf format
> > string, ./config.rpath not existing, and GDALmake.opt.in ignoring the
> > --datarootdir setting), and a look at the output indicates OpenCL
> > support is selected.
> > 
> > Compilation itself completes with no obvious errors, and the resulting
> > functions run correctly. However, there is no speedup from using -wo
> > "USE_OPENCL=TRUE" over -wo "USE_OPENCL=FALSE", nor is there any effect
> > seen using nvidia-smi monitoring.
> > 
> > The GDALWARP command I'm running is this:
> > gdalwarp -srcnodata 9999 -dstnodata 9999 -t_srs EPSG:4326 -of GTiff -tr
> > 0.03 0.03 -r cubicspline -multi -wo "USE_OPENCL=TRUE" tmp.grib2 tmp.tif
> > 
> > vs.
> > 
> > gdalwarp -srcnodata 9999 -dstnodata 9999 -t_srs EPSG:4326 -of GTiff -tr
> > 0.03 0.03 -r cubicspline -multi -wo "USE_OPENCL=FALSE" tmp.grib2 tmp.tif
> > 
> > 
> > This system has four cores and is multithreading, so -wo
> > "NUM_THREADS=ALL_CPUS" does produce a speedup. But again, USE_OPENCL
> > does not. In fact, the program is entirely functional and does exactly
> > what I want, except for opencl functionality.
> > 
> > I'm at a bit of a loss as to what might be wrong. I've tried various
> > combinations of the with-opencl flags. I'm running all functions as
> > root, and have tried modprobe nvidia-uvm. No errors, no debug problems
> > noted, it just won't use the GPU. Part of my problem is I'm not sure
> > what problems would produce an error, and what just would fail silently.
> > 
> > Any insight would be appreciated!
> > 
> > Best regards,
> > Jonathan Williams
> > _______________________________________________
> > gdal-dev mailing list
> > gdal-dev at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/gdal-dev
> 
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