OpenCL vs CUDA

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Asgaroth
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Joined: Sun Dec 09, 2018 12:06 am

OpenCL vs CUDA

Post by Asgaroth » Sat Dec 15, 2018 11:18 pm

Hi All,

Just a simple question, when the FaH client supported CUDA did it use less CPU cycles to drive the GPU's? It seems that OpenCL hammers the CPU's to feed the GPU's. I do have the CPU slot removed so the client is not using my CPU's at all to crunch work units.

I've done a quick search to see if I could find this answered elsewhere but my google-fu has failed me.

Thanks
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JimboPalmer
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Re: OpenCL vs CUDA

Post by JimboPalmer » Sun Dec 16, 2018 2:45 am

Yes. CUDA is Nvidia only. Nvidia's OpenCL driver does a 'busy wait' on one CPU, busy waiting is almost always a poor design. AMD does not use a busy wait, so draws less CPU.

The Pande Group has limited funds so has focused on a single GPU model, OpenCL. In the past, they supported multiple cores based on vendor specific platforms but at some additional cost. (Funded by Nvidia and AMD?)

In some theoretical world with infinite funds and infinite programmer support, multiple cores written for every variation would yield faster results. As it is, we are stuck with Nvidia's poor design choice. (If they can force you to use CUDA software, they have a monopoly on hardware)

It is somewhat excusable when GPU folding is 100s of times more points than CPU folding.

https://en.wikipedia.org/wiki/Busy_waiting

(In a past life I had a busy wait I could not avoid, but I could run it on any CPU on my network. I used the slowest device I could find. ARM has a similar feature called big.LITTLE, but x86 does not)
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Asgaroth
Posts: 14
Joined: Sun Dec 09, 2018 12:06 am

Re: OpenCL vs CUDA

Post by Asgaroth » Sun Dec 16, 2018 10:43 am

Thanks for the reply, I was just wondering if there would ever be an opportunity for nvidia users to use cuda only thereby freeing up the cpu to feed more gpu's (for example, amd gpu's). Based on your response above this appears that it is unlikely to happen.
There are two major products that came out of Berkeley: LSD and UNIX. We don't believe this to be a coincidence.
-- Jeremy S. Anderson

bruce
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Re: OpenCL vs CUDA

Post by bruce » Mon Dec 17, 2018 11:14 pm

A busy-wait process is designed to waste CPU power in a way that improves response time ... the latter being an important consideration for gamers who detest the extra overhead required to interrupt another process to get attention by the CPU. While a busy-wait appears to use a lot of CPU cycles, it's easily interrupted by another process -- and no interruption is required to begin processing work assigned to the GPU driver processes.

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