On 23.05.2014 14:17, Lukas Jirkovsky wrote: > Hello, > I've been toying with the idea of bumping libcl from version 1.1 to > 1.2. Bellow I will sum up my findings. > > Current State > ------------------- > The opencl support is split into three different packages: > > * opencl-headers - provides header files necessary for compilation, > currently at version 1.1 > > * libcl - provides libCL.so which is an ICD loader, ie. this > libraryis used to the actual OpenCL implementation depending on the > user needs. In arch we use proprietary libcl from the nVidia drivers. > Because nVidia supports only OpenCL 1.1 our library does, too. > > * opencl-nvidia - an OpenCL implementation. There are packages in > AUR that provide the implementation for other vendors, too, such as > intel-opencl-sdk > > There are two main reasons why our OpenCL support is stuck at 1.1: > * when the OpenCL support was introduced, libcl was only provided by > nVidia and AMD as part of their proprietary drivers, but AMD binary > drivers are not supported > * nvidia supports only OpenCL 1.1 > > Proposed Changes > ---------------------------- > The time has changed and now there are two opensource ICD loaders available: > * ocl-icd (https://aur.archlinux.org/packages/ocl-icd/) > * opencl-icd (https://aur.archlinux.org/packages/opencl-icd/) > Both ICD loaders provide libCL.so in version 1.2. Both ICD loaders are > drop-in replacements for the current libcl, ie. no rebuild is needed. > > I propose the following changes: > 1. Update the opencl-headers to 1.2 (again). There is a package > opencl-headers12 that grabs them from svn. > 2. replace libcl with either ocl-icd or opencl-icd > > Reasons for change: > * replace proprietary libCL.so with an open source one > * support for OpenCL 1.2. While nVidia doesn't support this, it will > allow using OpenCL 1.2 features on devices that support it (Intel > CPU's, AMD GPU's) which couldn't have been used before as they were > not provided by libCL > > Possible Problems > --------------------------- > So far I was able to find only one possible problem. Applications > using OpenCL has to check for the supported OpenCL version on runtime. > However, if an application does the check only on compile time, it > will crash. IIRC this used to be a problem with luxmark, but I tested > it and it works correctly now. I have also tested imagemagick and > blender and both work fine. Well, blender is broken for me, but it was > before, too. At least it doesn't crash. > > In more detail, the reason is that you can compile OpenCL 1.2 > application without problems even on OpenCL 1.1 system as the > libraries and headers will now provide everything needed. However, if > the application tries to call an OpenCL 1.2 function, the driver will > not provide it, in which case it will crash. > > In any case if such issue arises, it needs to be fixed upstream. > > The BIG Question > -------------------------- > We once had problem that there were no suitable ICD loaders part the > one from nVidia. Now we have two. The question is which one to use. > > * opencl-icd is the reference ICD loader from Khronos. It uses a > custom license (or at least a license I don't know) which seems to > forbid distributing of sources, but which explicitly allows > redistribution of the compiled binaries > > * ocl-icd is an independent project under 2-clause BSD license. I > think from the two this one has longer development > > Lukas +1 for the idea.
As for which loader to use, I have no idea. Pick the saner one.
