CPU folding on iGPU?

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CPU folding on iGPU?

Postby foldy » Sat Apr 13, 2019 11:51 am

Latest Gromacs 2019 now supports offload of tasks to CPU integrated iGPUs using OpenCL 1.2.

So maybe a next FahCore_a8 for CPU could use the Intel or AMD CPU integrated iGPU to help CPU folding?
As these iGPUs were mostly too slow for GPU folding they finally could be used to help CPU. :?:

http://manual.gromacs.org/documentation ... mance.html
PME long-ranged interaction GPU offload now available with OpenCL

On supported devices from all supported vendors (AMD, Intel, NVIDIA), it is now possible to offload PME tasks to the GPU using OpenCL. This works in the same way as the former CUDA offload. A single GPU can now be used to accelerate the computation of the long-ranged PME interactions. This feature means that only 2-4 CPU cores per GPU will be about as fast as the 2018 version that needed many more CPU cores to balance the GPU. Performance on hardware that had good balance of GPU and CPU also shows minor improvements, and the capacity for hardware with strong GPUs to run effective simulations is now greatly improved.
Intel integrated GPUs are now supported for GPU offload with OpenCL

On Intel CPUs with integrated GPUs, it is now possible to offload nonbonded tasks to the GPU the same way as offload is done to other GPU architectures. This can have performance benefits, in particular on modern desktop and mobile Intel CPUs this offload can give up to 20% higher simulation performance.
Last edited by foldy on Sun Apr 14, 2019 2:11 pm, edited 1 time in total.
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Re: CPU folding on iGPU?

Postby toTOW » Sat Apr 13, 2019 12:04 pm

I think we never used Gromacs for GPU in FAH ... GPU cores are based on OpenMM.
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Re: CPU folding on iGPU?

Postby foldy » Sat Apr 13, 2019 2:15 pm

I know the OpenMM based FAH GPU cores do not run on the CPU integrated iGPUs. But now the Gromacs 2019 allows a CPU core to use the CPU integrated iGPU. So the iGPU is seen similar to the CPU SSE or AVX extensions. New gromacs supports iGPU and FAH does not yet use iGPU - so bring it together :-)
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Re: CPU folding on iGPU?

Postby bruce » Sat Apr 13, 2019 4:59 pm

You might check and see if this is included in enhancement list for OpenMM when the short-range forces are being processed on the GPU.
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Re: CPU folding on iGPU?

Postby toTOW » Sat Apr 13, 2019 6:57 pm

I've seen some BOINC projects trying to use Gromacs on CPU and GPU simultaneously, but it was never very efficient ... :(
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Re: CPU folding on iGPU?

Postby foldy » Sat Apr 13, 2019 8:45 pm

Gromacs says upto 20% speedup when using CPU's iGPU compared to CPU only. It seems similar to using CPU's SSE or AVX units to get a speedup. Efficiency in power usage I don't know if it also gets 20% more power usage? I like the approach as currently iGPUs are idle now could be used to speedup CPU folding.
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Re: CPU folding on iGPU?

Postby MeeLee » Sun Apr 14, 2019 12:34 pm

Would one CPU core be assigned to the IGP, or does the system work different from DGPU cards?
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Re: CPU folding on iGPU?

Postby toTOW » Sun Apr 14, 2019 1:12 pm

The problem on these hybrid cores is that you can't know easily if it is an iGPU to use with the CPU or a discrete GPU that you shouldn't use and leave free for a full GPU core ...

Using a discrete GPU with an hybrid core would be a waste of resources : the GPU would wait a lot for work from the CPU. It's what I saw on BOINC projects that tested this solution ...

I guess that's the reason why FAH never used this kind of solutions.
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Re: CPU folding on iGPU?

Postby foldy » Sun Apr 14, 2019 1:48 pm

toTOW wrote:The problem on these hybrid cores is that you can't know easily if it is an iGPU to use with the CPU or a discrete GPU that you shouldn't use and leave free for a full GPU core ...

It can be decided by GPU vendor:
* Intel iGPU is not supported by FAH OpenMM core => so use it for FAH CPU core.
* NVidia does not have an iGPU so use nvidia GPU for FAH OpenMM core only.
* AMD has both discrete GPU and iGPU. You can decide by device part number.

Similar to GPUs being too slow or not supported by FAH OpenMM core there would be a list of integrated iGPUs which are supported by FAH CPU core or not. Maybe even some discrete GPUs which are too slow or old for FAH OpenMM core could help the CPU instead.

I hope it is easy to setup by just telling a future FAH Gromacs 2019 CPU core to use an existing iGPU or not.
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Re: CPU folding on iGPU?

Postby MeeLee » Sun Apr 14, 2019 4:07 pm

If I would guesstimate,
I'd say that older CPU cores with IGPs, usually have 4 to 12 cores running between 400-900Mhz.
If 1 CPU core at 2Ghz is lost to feeding the IGP, in worst case scenario you'd be trading a 2Ghz thread for a 1,6Ghz thread (4 cores at 400Mhz), and actually would lose performance compared to running both CPU cores to fold.
At best, you'd run an equivalent of about 10Ghz on the IGP (if it had 12 cores running at 900Mhz); and speeds would increase to an equivalent of 4Ghz to 12Ghz; and it would triple performance.
At first it would look worthwhile, however, older APUs would probably rise from 1-3k PPD to 3-9k PPD. I don't think it would make much sense doing the research on those.

A modern CPU, like the AMD Ryzen 5 2400G running 4 cores of 3.6GHz (or a theoretical 14.4 Ghz performance), would trade one CPU core for 11 GPU cores running at 1250Mhz, or a theoretical trade in of 3.6Ghz for 13.75Ghz; would increase performance by 70%.
Not a lot of information out there on CPU folding numbers on the new Ryzens, but many mention that the IGP's speed is a lot slower than a similarly clocked DGPU, due to the much slower RAM.
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