On Fri, May 15, 2020, at 8:52 PM, hritikesh semwal via discuss wrote:

Hello,

I am working on a parallel CFD solver with MPI and I am using an account on a cluster to run my executable. The hardware structure of my account is as follows;

Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 32 On-line CPU(s) list: 0-31 Thread(s) per core: 2 Core(s) per socket: 8 CPU socket(s): 2 NUMA node(s): 2 Vendor ID: GenuineIntel CPU family: 6 Model: 62 Stepping: 4 CPU MHz: 2600.079 BogoMIPS: 5199.25 Virtualization: VT-x L1d cache: 32K L1i cache: 32K L2 cache: 256K L3 cache: 20480K NUMA node0 CPU(s): 0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30 NUMA node1 CPU(s): 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31

Initially, I was running my executable with any binding options and in that case, whenever I was switching from 2 to 4 processors my computation time was also increasing along with communication time inside some iterative loop.

Today, somewhere I read about binding options in MPI through which I can manage the allocation of processors. Initially, I used the "-bind-to core" option and the results were different and I got time reduction up to 16 processors and after that with 24 and 32 processors, it has started increasing. Results of timing are as follows; 2 procs- 160 seconds, 4 procs- 84 seconds, 8 procs- 45 seconds, 16 procs- 28 seconds, 24 procs- 38 seconds, 32 procs- 34 seconds.

After that, I used some other combinations of binding option but did not get better timing results compared to -bind-to core option. So, I back edited the bind to option to core but now I am getting different timing results with the same executable which are as follows, 2 procs- 164 seconds, 4 procs- 85 seconds, 8 procs- 45 seconds, 16 procs- 48 seconds, 24 procs- 52 seconds, 32 seconds- 98 seconds.

Hitesh, You might find the following online workshop useful: http://www.hlrs.de/training/2020-05-25-VI-HPS/ Regards, Benson