OpenCL

[FangQ]

My Threadripper 3990X based servers (10-nodes) have arrived and I am looking for the OpenCL driver to run some benchmarks. The servers run Ubuntu 20.04 with NVIDIA GPU drivers. I googled and could not find a driver for this CPU, does it exist?

similarly, I was also not able to run OpenCL on a Ryzen9 3950x desktop CPU.

any pointer on this is appreciated!

[dipak]

AMD dropped OpenCL support for CPU more than year ago.  Hence, with the recent drivers, CPU is no longer recognized as OpenCL device.

As I know, here is an open-source OpenCL implementation that supports CPUs:  pocl - Portable Computing Language .  You may use this package to access CPU devices. 

Thanks.

[FangQ]

thanks, just tried pocl on one of my machines running Ryzen9 3950X (16 core), unfortunately its speed is approximately the same as Ryzen 1700X (8 core) running on AMD's OpenCL CPU driver , see http://mcx.space/computebench/ 

2020-8-5	fangq	/ pthread-AMD Ryzen 9 3950X 16-Core Processor / hoyi(pocl 1.2 Ryzen9 3950X)	1368
2019-3-4	fangq	/ AMD Ryzen 7 1700X Eight-Core Processor / zen	1325

I suppose the 3rd party driver in pocl is far less (2x) efficient than the vendor driver.

is there a way I can still run the old AMD CPU driver on these new CPUs?

[dipak]

CPU support was provided by the AMD APPSDK, which is not compatible with AMDGPU-Pro. If you want to try this SDK, then please use a compatible driver (and OS) with it. Please note, AMD APPSDK is no longer supported and we do not recommend it anymore. 

Another point is, APP SDK was not tuned for Zen and newer CPU architectures, hence you may not observe expected performance gain using it. For example, here is a old post where someone reported a performance issue using OpenCL on EPYC: OpenCL issues on EPYC 7551 

Thanks.

[FangQ]

thanks @dipack, can you provide me a download link to AMD APPSDK for Linux? all links I found online are broken - also, my system currently has nvidia gpu and driver, can APPSDK just install opencl support for the CPU without removing my existing gpu driver?

[dipak]

Sorry, I can't provide you any download link for  AMD APPSDK because the SDK package and related pages and links were officially removed from the AMD website. As a result, most of the download links are broken now.

Regarding your other query, the OpenCL CPU runtime is part of the AMD APPSDK, so it is expected to work as a standalone package to access the CPU devices. 

Thanks.

[FangQ]

@dipak, thanks again for your prompt reply. I managed to download a copy of APPSDK from this link: 

AMD LINUX - Download AMD driver and SDK · GitHub 

clinfo and my program both managed to see my AMD Ryzen Threadripper 3990X processor on the platform "AMD Accelerated Parallel Processing", however, when running the simulation, I got an error:

```

Kernel build log:
Internal error: Compilation init failed.

```

it has no problem running on pocl on this CPU (as well as on other devices, such as Vega10/20 via ROCm). 

do you think this is an installation issue or compatibility issue of APPSDK?

[dipak]

Yes, it could be an installation/compatibility issue. Actually APPSDK was never tested on these newer setups, so it's difficult say what might be the exact issue here.