[Wily] nvidia-libopencl1-* not installable

> while looking at the nvidia packages I noticed that all
> nvidia-libopencl1-* packages want to replace and provide libopencl1,

That is correct, you can only have one libopencl1 (OpenCL ICD Loader) package installed.
In most circumstances you would have ocl-icd-libopencl1, but if you manually installed nvidia-libopencl1-352, it should remove any other OpenCL ICD Loader.

You can however, have multiple OpenCL ICDs installed, and nvidia-opencl-icd-352 is one of these.

Please tell me what OpenCL packages you had installed, what you were trying to install, and what apt wanted to remove.

So far there are not much applications and libraries using opencl, but I fall into this when just trying to install clinfo (Just a simple testing application like vainfo or vdpauinfo) with nvidia-libopencl1-*.

As you can see it also affects wine1.6.

thopiekar@home:~$ LANG=C sudo apt-get install nvidia-libopencl1-352
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libcublas6.5 libcudart6.5 libcufft6.5 libcufftw6.5 libcuinj64-6.5 libcurand6.5 libcusparse6.5 libnppc6.5 libnppi6.5 libnpps6.5 libnvblas6.5 libnvtoolsext1 libnvvm2 libthrust-dev
  libvdpau-dev nvidia-cuda-dev nvidia-cuda-doc nvidia-cuda-gdb nvidia-profiler nvidia-visual-profiler opencl-headers
Use 'apt-get autoremove' to remove them.
The following packages will be REMOVED:
  clinfo libhwloc-plugins nvidia-cuda-toolkit nvidia-opencl-dev ocl-icd-libopencl1 ocl-icd-libopencl1:i386 wine1.6 wine1.6-amd64 wine1.6-i386:i386
The following NEW packages will be installed:
  nvidia-libopencl1-352
0 upgraded, 1 newly installed, 9 to remove and 5 not upgraded.
Need to get 18,9 kB of archives.
After this operation, 296 MB disk space will be freed.
Do you want to continue? [Y/n] n
Abort.

Btw. this problem might also be present in Vivid, I guess.

> thopiekar@home:~$ LANG=C sudo apt-get install nvidia-libopencl1-352

There is your problem. Everything in the archive that uses OpenCL was compiled against ocl-icd-libopencl1, so you need that.
You shouldn't ever need to install nvidia-libopencl1-352.

The ocl-icd-libopencl1 OpenCL ICD Loader is capable of loading nvidia-opencl-icd-352 (and any other OpenCL ICD in the archive).

So, why does clinfo say that there are no devices?
If you are right I would expect there some output about my GPU.

Is ocl-icd-libopencl1 not properly finding the ICD?

> So, why does clinfo say that there are no devices?

Try:
$ sudo apt-get install nvidia-modprobe
$ clinfo

Works! So, wouldn't it be a good idea making nvidia-opencl-icd-* at least recommend to install nvidia-modprobe? Other people won't get confused like me trying to install the nvidia-libopencl1-*, too.

thopiekar@home:~$ clinfo
Number of platforms 1
  Platform Name NVIDIA CUDA
  Platform Vendor NVIDIA Corporation
  Platform Version OpenCL 1.2 CUDA 7.5.18
  Platform Profile FULL_PROFILE
  Platform Extensions cl_khr_byte_addressable_store cl_khr_icd cl_khr_gl_sharing cl_nv_compiler_options cl_nv_device_attribute_query cl_nv_pragma_unroll cl_nv_copy_opts
  Platform Extensions function suffix NV

  Platform Name NVIDIA CUDA
Number of devices 1
  Device Name GeForce GT 720
  Device Vendor NVIDIA Corporation
  Device Vendor ID 0x10de
  Device Version OpenCL 1.2 CUDA
  Driver Version 352.41
  Device OpenCL C Version OpenCL C 1.2
  Device Type GPU
  Device Profile FULL_PROFILE
  Device Topology (NV) PCI-E, 02:00.0
  Max compute units 1
  Max clock frequency 797MHz
  Compute Capability (NV) 3.5
  Device Partition (core)
    Max number of sub-devices 1
    Supported partition types None
  Max work item dimensions 3
  Max work item sizes 1024x1024x64
  Max work group size 1024
  Preferred work group size multiple 32
  Warp size (NV) 32
  Preferred / native vector sizes
    char 1 / 1
    short 1 / 1
    int 1 / 1
    long 1 / 1
    half 0 / 0 (n/a)
    float 1 / 1
    double 1 / 1 (cl_khr_fp64)
  Half-precision Floating-point support (n/a)
  Single-precision Floating-point support (core)
    Denormals Yes ...

> Works!

Glad to hear it!

> So, wouldn't it be a good idea making nvidia-opencl-icd-* at least
> recommend to install nvidia-modprobe? Other people won't get
> confused like me trying to install the nvidia-libopencl1-*, too.

We would like to have nvidia-graphics-drivers-* recommend nvidia-modprobe, or provide some way of automatically loading the kernel modules and creating the device nodes. The nvidia-modprobe package is currently in 'universe' and would need to be included in 'main' before a package in 'restricted' can depend on or recommend it.

I'm going to mark this as a duplicate of the bug where we are tracking that.