From: Josh Vermaas (joshua.vermaas_at_gmail.com)
Date: Thu Jun 04 2020 - 14:59:36 CDT
Hi Raman,
Yes, although the effectiveness for this is mixed. For NAMD 2.X, a
multicore build will use all the GPUs it sees, and to my knowledge does not
use SLI. This leads us to the answer to #2 as well. NAMD will get better
performance the more GPUs you throw at the problem, up to a limit of how
fast your PCI transfers are. For the 2.X branch, this cap is pretty low,
and usually what I do instead is to run multiple jobs with only 1 GPU
(using the +devices argument to make sure every simulation gets their own
GPU) and as many CPUs as I can give it (the integrator is on the CPU, and
on modern hardware is rate limiting). Since mining rigs are usually GPU
heavy, you may want to try the alpha NAMD 3.X line, which leaves more of
the work on the GPU and basically just uses the CPU to launch GPU tasks.
The 3.X line right now can only use 1 GPU per simulation, so it effectively
replicates the cryptocurrency workflow of "1 GPU per thing", but NAMD 3.X
has had some pretty good performance in my own testing.
-Josh
On Thu, Jun 4, 2020 at 11:59 AM Raman Preet Singh <
ramanpreetsingh_at_hotmail.com> wrote:
> Dear All,
>
>
>
> I am looking towards building a cheap computer for MD using cheap and
> second-hand components. The systems that I am interested in studying are
> typically below 25K atoms so there is no need for very large number of
> compute cores.
>
>
>
> In one such consumer desktop, I could get performance close to 40 ns/day
> using a consumer GPU 1050 Ti. However, when I tried attaching another 1050
> Ti (motherboard has 3 PCI slots), it was not detected by NAMD. The OS,
> 64-bit Win 10, too showed issues with one of the two GPUs. Reading through
> loads of forums and tech documents I found that the said motherboard
> detects more than 1 GPU only if the GPUs support SLI. 1050 Ti is a non-SLI
> GPU.
>
>
>
> When I tried these two GPUs in a motherboard used for cryptocurrency
> mining, the OS (64-bit Win 10) and NAMD were able to detect the two GPUs.
> As expected, these were identified as device 0 and 1 by NAMD. However, I
> could not confirm performance gain as the processor was a low throughput
> one and apparently 1 GPU was enough to obtain the maximum performance.
>
>
>
> Reading through several websites, I found that SLI combines the
> performance of multiple GPUs to produce a single output. Cryptocurrency
> algorithms break the job in multiple instances and each instance is run
> individually on a GPU and the output of all the GPUs is then combined –
> hence, non-SLI GPUs work independently in a mining rig. While searching for
> GPU support in NAMD, I could not find any specific reference to SLI or
> non-SLI cards.
>
>
>
> My questions are:
>
> 1. Does NAMD support multiple non-SLI GPUs?
> 2. Can two or three non-SLI consumer GPUs (1050 Ti), when included in
> a mining rig with 8/16-core processor, be used for performance improvement
> of NAMD?
>
>
>
> Regards,
>
> Raman
>
>
>
>
>
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