OpenCL support for Xeon Phi processor (Knights Landing architecture)

[Viktor_R_]

Hi,

Is OpenCL supported on the newer Xeon Phi processors? The most definite information that I found that it's not supported is a post from 2 years ago (https://software.intel.com/en-us/forums/opencl/topic/697753). Has anything changed since?

Thanks,

Viktor

[Henry_G_Intel]

Hi Viktor,

According to the release notes, the Intel SDK for OpenCL Applications does not support Xeon Phi. Intel Code Builder for OpenCL API supports offload to Xeon Phi coprocessors but it doesn't appear to support Xeon Phi hosts. The OpenCL forum on Intel Developer Zone might have more information.

Best regards,

Henry

[P__Robert]

OpenCL driver for all Xeon Phi coprocessors [x100 and x200]?

[JJK]

I've asked this question (what about OpenCL support for Xeon Phi x100 and x200?) several times at Intel meetings, and never got a satisfactory answer... it seems Intel is promoting support for OpenCL on every product (desktop CPUs incl their GPUs, server CPUs, FPGA chips) except for the Xeon Phi's.

In short:

• The Xeon Phi x100 range supported (supports) OpenCL but performance is mediocre; rewriting your code using OpenMP is more effective. Also, note that OpenCL support for the x100 range has officially been ended.
• The Xeon Phi x200 CPU series (non PCI-e) behave like regular CPUs yet they are not supported using Intel's own OpenCL CPU driver, which does support Atom, Core i5/6/7, etc.
• With a lot of trickery, it is possible to get OpenCL code running on the Xeon Phi x200 CPU, using either AMD's (!!) APP kit, which is very slow, or using an older version of the Intel OpenCL driver, which does not support AVX2 or AVX512 (i.e. it's also slow)
• The Xeon Phi x200 PCI-e card have gone AWOL as per July 20th or so, so it's impossible to tell if OpenCL support for those cards is achievable (though it would never be supported by Intel)

This all seems to be a software design decision by Intel, not a hardware issue. I'd be very interested to talk to an Intel OpenCL Developer on some hidden tweaks to get AVX512 working in the OpenCL autovectorizing engine for the Xeon Phi.

PS a post about NVidia supporting also seems to have gone AWOL; my note on that would be:   NVidia's support for OpenCL is abysmal; yes they support it, but performance is very poor. Note also that they've thrown out all OpenCL SDK stuff from both the driver and the Cuda SDK.

[JJK · Accepted solution]

To follow up on my own comment:

Intel has now released the "intel_sdk_for_opencl_2017_7.0.0.2511_x64" , which includes "Intel CPU experimental 2.1 runtime for OpenCL(TM) application's development". And yessss, this one does support the KNL processor, although performance is NOT what I was hoping for - perhaps there are some tweaks to apply, but without any special flags the Xeon Phi 7210 is about as fast a single (Broadwell) Xeon E5 2690v4.

[Viktor_R_]

Hi JJK,

Thanks for the update, that is indeed very interesting! I assume that this is strictly experimental and not really advertised by Intel. I could not find Xeon Phi support listed in the OpenCL 2017 release notes (https://software.intel.com/file/559106/download). But maybe I overlooked it?

Best,
Viktor

[user1900]

Any update?

I am struggling to get the latest OpenCL driver for Intel Xeon Phi. I have a Knights Corner (KNC) and I only find the deprecated OpenCL Runtime 14.2 (from 2014?). Where can I find the non deprecated release?

Website: https://software.intel.com/en-us/articles/opencl-drivers

If I download the latest Intel OpenCL SDK for Applications, I only get support for the Xeon, but not for the Xeon Phi.

So far the only way to get my KNC detected is with the OpenCL Runtime 14.2.

[Viktor_R_]

Hi user1900.

The only OpenCL runtime for KNC is the deprecated one. JJK says above that recent OpenCL runtimes also support KNL experimentally but I have not tried that.

Regards,

Viktor

[user1900]

Thanks ;)

[Pawel_E_]

hi everyone,

I'm trying opencl_runtime_16.1.2_x64_rh_6.4.0.37.tgz as site says: 13 Dec 2017 in hope clinfo would show my Phis but there are not there.

Would you know if that package version supports Xeon Phi?

many thanks, P.