Hi,

to bring a bit of input to the different topics.

darktable needs the system library libOpenCL.so which must be accessible 
to the system's dynamic loader (ld.so). Reason is that the function flow 
is like this:

darktable -> libOpenCL.so -> libnvidia-opencl.so.1 -> kernel driver -> 
hardware

There is no way of bypassing libOpenCL.so by directly calling 
libnvidia-opencl.so.1 because the two are different.

Depending on your system you will need to install the right packages to 
get libOpenCL.so - typically a chain of symbolic links to something like 
libOpenCL.so.x.y.z. Try 'locate libOpenCL.so' to see if the symbolic 
link(s) exist.

@Istvan: you are probably still missing that library or ld.so can't find it.

If the library is found there are other requirements that must be met.

As written above you need the vendor specific library 
libnvidia-opencl.so.1 (or similar). libOpenCL.so knows from the content 
of /etc/OpenCL/vendors/nvidia.icd which vendor library to call. If that 
file is missing, OpenCL can't work.

Then the kernel driver needs to be loaded. Newer nvidia systems need two 
kernel modules: nvidia and nvidia_uvm.

Check with 'lsmod | egrep nvidia' if both are there.

If this is OK there need to be device special files for the vendor 
specific library to communicate with your kernel drivers. You need to 
see something like that:

crw-rw----+ 1 root video 195,   0 24. Jul 18:28 /dev/nvidia0
crw-rw----+ 1 root video 195, 255 24. Jul 18:28 /dev/nvidiactl
crw-rw-rw-  1 root root  249,   0 24. Jul 18:28 /dev/nvidia-uvm

Check that your account has write access to all of them. In my case 
users who want to use OpenCL need to be member of group video.

@Federico:

The error number -1001 from your system tells that even though you have 
libOpenCL.so one of the other requirements above were not met.

Ulrich



Am 24.07.2014 13:53, schrieb Federico Bruni:
> Il 24.07.2014 07:15 Ulrich Pegelow ha scritto:
>> You are lacking libOpenCL.so which should be a symbolic link to
>> libOpenCL.so.1. We had a similar issue before.
>>
>> Normally this link gets generated during installation of the driver by
>> automatically calling ldconfig. You may either
>>
>> * call ldconfig as root (preferred option)
>> * generate the link manually
>>
>
> Same problem here, but ldconfig did not help to generate the symlink.
> Output from root user:
>
> # find / -name 'libOpenCL.so'
> #
> # ldconfig
> # find / -name 'libOpenCL.so'
> #
>
> It seems that it should be included in this package:
>
> $ apt-file search libOpenCL.so | grep nvidia
> nvidia-libopencl1: /usr/lib/x86_64-linux-gnu/libOpenCL.so
> nvidia-libopencl1: /usr/lib/x86_64-linux-gnu/libOpenCL.so.1
> nvidia-libopencl1: /usr/lib/x86_64-linux-gnu/libOpenCL.so.1.0.0
> nvidia-opencl-dev: /usr/lib/x86_64-linux-gnu/libOpenCL.so
>
> But it's actually just in nvidia-opencl-dev:
> https://packages.debian.org/sid/amd64/nvidia-opencl-dev/filelist
> https://packages.debian.org/sid/amd64/nvidia-libopencl1/filelist
>
> Now I've installed the -dev package and I got the symlink:
>
> $ ls -l /usr/lib/x86_64-linux-gnu/libOpenCL.so
> lrwxrwxrwx 1 root root 14 mag 25 01:36
> /usr/lib/x86_64-linux-gnu/libOpenCL.so -> libOpenCL.so.1
>
> However, darktable can't use opencl:
>
> [opencl_init] trying to load opencl library: '<system default>'
> [opencl_init] opencl library 'libOpenCL' found on your system and loaded
> [opencl_init] could not get platforms: -1001
> [opencl_init] FINALLY: opencl is NOT AVAILABLE on this system.
> [opencl_init] initial status of opencl enabled flag is OFF.
>
> I'm on debian sid. I've reported the problem here weeks ago:
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=746643
>
> $ cat /proc/driver/nvidia/version
> NVRM version: NVIDIA UNIX x86_64 Kernel Module  340.24  Wed Jul  2
> 14:24:20 PDT 2014
> GCC version:  gcc version 4.8.3 (Debian 4.8.3-4)
>
>

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