[gmx-users] Can we set the number of pure PME nodes when using GPU&CPU?

Fri Aug 22 10:11:12 CEST 2014

Hi Mark,

Could you tell me why that when we are GPU-CPU nodes as PME-dedicated 
nodes, the GPU on such nodes will be idle?

Theo

On 8/11/2014 9:36 PM, Mark Abraham wrote:
> Hi,
>
> What Carsten said, if running on nodes that have GPUs.
>
> If running on a mixed setup (some nodes with GPU, some not), then arranging
> your MPI environment to place PME ranks on CPU-only nodes is probably
> worthwhile. For example, all your PP ranks first, mapped to GPU nodes, then
> all your PME ranks, mapped to CPU-only nodes, and then use mdrun -ddorder
> pp_pme.
>
> Mark
>
>
> On Mon, Aug 11, 2014 at 2:45 AM, Theodore Si <sjyzhxw at gmail.com> wrote:
>
>> Hi Mark,
>>
>> This is information of our cluster, could you give us some advice as
>> regards to our cluster so that we can make GMX run faster on our system?
>>
>> Each CPU node has 2 CPUs and each GPU node has 2 CPUs and 2 Nvidia K20M
>>
>>
>> Device Name     Device Type     Specifications  Number
>> CPU Node        IntelH2216JFFKRNodes    CPU: 2×Intel Xeon E5-2670(8 Cores,
>> 2.6GHz, 20MB Cache, 8.0GT)
>> Mem: 64GB(8×8GB) ECC Registered DDR3 1600MHz Samsung Memory     332
>> Fat Node        IntelH2216WPFKRNodes    CPU: 2×Intel Xeon E5-2670(8 Cores,
>> 2.6GHz, 20MB Cache, 8.0GT)
>> Mem: 256G(16×16G) ECC Registered DDR3 1600MHz Samsung Memory    20
>> GPU Node        IntelR2208GZ4GC         CPU: 2×Intel Xeon E5-2670(8 Cores,
>> 2.6GHz, 20MB Cache, 8.0GT)
>> Mem: 64GB(8×8GB) ECC Registered DDR3 1600MHz Samsung Memory     50
>> MIC Node        IntelR2208GZ4GC         CPU: 2×Intel Xeon E5-2670(8 Cores,
>> 2.6GHz, 20MB Cache, 8.0GT)
>> Mem: 64GB(8×8GB) ECC Registered DDR3 1600MHz Samsung Memory     5
>> Computing Network Switch        Mellanox Infiniband FDR Core Switch
>> 648× FDR Core Switch MSX6536-10R, Mellanox Unified Fabric Manager       1
>> Mellanox SX1036 40Gb Switch     36× 40Gb Ethernet Switch SX1036, 36× QSFP
>> Interface     1
>> Management Network Switch       Extreme Summit X440-48t-10G 2-layer Switch
>> 48× 1Giga Switch Summit X440-48t-10G, authorized by ExtremeXOS       9
>> Extreme Summit X650-24X 3-layer Switch  24× 10Giga 3-layer Ethernet Switch
>> Summit X650-24X, authorized by ExtremeXOS    1
>> Parallel Storage        DDN Parallel Storage System     DDN SFA12K Storage
>> System       1
>> GPU     GPU Accelerator         NVIDIA Tesla Kepler K20M        70
>> MIC     MIC     Intel Xeon Phi 5110P Knights Corner     10
>> 40Gb Ethernet Card      MCX314A-BCBT    Mellanox ConnextX-3 Chip 40Gb
>> Ethernet Card
>> 2× 40Gb Ethernet ports, enough QSFP cables      16
>> SSD     Intel SSD910    Intel SSD910 Disk, 400GB, PCIE  80
>>
>>
>>
>>
>>
>>
>>
>> On 8/10/2014 5:50 AM, Mark Abraham wrote:
>>
>>> That's not what I said.... "You can set..."
>>>
>>> -npme behaves the same whether or not GPUs are in use. Using separate
>>> ranks
>>> for PME caters to trying to minimize the cost of the all-to-all
>>> communication of the 3DFFT. That's still relevant when using GPUs, but if
>>> separate PME ranks are used, any GPUs on nodes that only have PME ranks
>>> are
>>> left idle. The most effective approach depends critically on the hardware
>>> and simulation setup, and whether you pay money for your hardware.
>>>
>>> Mark
>>>
>>>
>>> On Sat, Aug 9, 2014 at 2:56 AM, Theodore Si <sjyzhxw at gmail.com> wrote:
>>>
>>>   Hi,
>>>> You mean no matter we use GPU acceleration or not, -npme is just a
>>>> reference?
>>>> Why we can't set that to a exact value?
>>>>
>>>>
>>>> On 8/9/2014 5:14 AM, Mark Abraham wrote:
>>>>
>>>>   You can set the number of PME-only ranks with -npme. Whether it's useful
>>>>> is
>>>>> another matter :-) The CPU-based PME offload and the GPU-based PP
>>>>> offload
>>>>> do not combine very well.
>>>>>
>>>>> Mark
>>>>>
>>>>>
>>>>> On Fri, Aug 8, 2014 at 7:24 AM, Theodore Si <sjyzhxw at gmail.com> wrote:
>>>>>
>>>>>    Hi,
>>>>>
>>>>>> Can we set the number manually with -npme when using GPU acceleration?
>>>>>>
>>>>>>
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