Re: max number of CPU PEs per GPU?

From: Jim Phillips (jim_at_ks.uiuc.edu)
Date: Sat Jun 11 2011 - 14:12:35 CDT

Definitely not this month. -Jim

On Fri, 10 Jun 2011, Danny Xu wrote:

> Jim,
>
> When will be the CUDA 4.0 NAMD version coming out?
>
> DX
>
>
>
> ________________________________
> From: Jim Phillips <jim_at_ks.uiuc.edu>
> To: Danny Xu <quantum_mania_at_yahoo.com>
> Cc: namd-l <namd-l_at_ks.uiuc.edu>
> Sent: Fri, June 10, 2011 12:15:19 PM
> Subject: Re: namd-l: max number of CPU PEs per GPU?
>
>
> You're probably hitting some driver limit on the number of client
> processes that can connect to a single GPU. With CUDA 4.0 we'll be moving
> to a multi-threaded model that will share GPUs more efficiently that
> should eliminate this issue. Even then 48 Opteron cores might not get any
> benefit from a single GPU.
>
> -Jim
>
>
> On Thu, 9 Jun 2011, Danny Xu wrote:
>
>> Hi,
>>
>> I was testing the namd 2.8b2 cuda binary (Linux-x86_64-CUDA) on a 48-core
>> opteron/1x GTX480 server. I got:
>> ...
>> Pe 41 sharing CUDA device 0 first 0 next 42
>> Pe 40 sharing CUDA device 0 first 0 next 41
>> FATAL ERROR: CUDA error cudaStreamCreate on Pe 23 (chili device 0): no
>> CUDA-capable device is available
>> ------------- Processor 23 Exiting: Called CmiAbort ------------
>> Reason: FATAL ERROR: CUDA error cudaStreamCreate on Pe 23 (chili device 0): no
>> CUDA-capable device is available
>>
>> First I thought there was something wrong with the GTX480 card. Then I tried
> 12
>> PE's and the job ran just fine. It turned out the max number core I could use
>> with one GTX480 is 14. My question is, is this hard coded in namd 2.8? Or it's
>> a
>> bug in 2.8b2 and has been fixed in 2.8?
>>
>> It'd be nice if all 48-core could be used with the GPU.
>>
>> Thanks,
>>
>> DX

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