[Mvapich-discuss] Question on shared memory communication

[Subramoni, Hari]

Hi, Zhiting.

Please accept our sincere apologies for the delay.

The correct channel for MVAPICH2 2.3.7 is ch3:mrail. The Nemesis netmod is an older, depreciated version.

The environment variable MV2_USE_SHMEM_COLL enables and disables the use of our hierarchical process topology aware collective communication schemes.

If you would like to disable CMA support, please set the environment variable MV2_USE_SMP_CMA=0 at runtime.

Several of these designs have been implemented in various MVAPICH libraries.

Best,
Hari.

From: Mvapich-discuss <mvapich-discuss-bounces+subramon=cse.ohio-state.edu at lists.osu.edu> On Behalf Of zhiting zhu via Mvapich-discuss
Sent: Friday, April 7, 2023 7:58 PM
To: Mvapich-discuss at lists.osu.edu
Subject: [Mvapich-discuss] Question on shared memory communication

Hi, I'm a new user of the MPI lib. I have a few questions.   - I notice that in the feature page for shared memory communication, there're two options:  Shared-Memory-CH3 and Shared-Memory-Nemesis. The descriptions are exactly the same. 
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Hi,

I'm a new user of the MPI lib. I have a few questions.

- I notice that in the feature page for shared memory communication, there're two options: Shared-Memory-CH3 and Shared-Memory-Nemesis. The descriptions are exactly the same. What's the difference between these two? I find that in the documentation MV2_USE_SHMEM_COLL applies to OFA-IB-CH3 and OFA-iWARP-CH3. It seems I have to use shared-memory-ch3?

FFLAGS="-w -fallow-argument-mismatch -O2" ../configure --with-device=ch3:mrail --disable-shared --prefix=$SCRIPT_DIR/mvapich2_install/

- I found a description on what nemesis is: https://www.mcs.anl.gov/uploads/cels/papers/TM-292.pdf<https://urldefense.com/v3/__https:/www.mcs.anl.gov/uploads/cels/papers/TM-292.pdf__;!!KGKeukY!x9GebWlzOwJDIaxL9-bETHPm371fheTuZHtVSJ15G3kugdUOeEYmtRp9BpmzRGMtI9WUiPHAwYNL56dSdR9oXMi1td2HJ6HR$> Is there any documentation about the shared memory algorithms used in ch3:mrail? I'm looking for the case that doesn't use CMA/XPMEM/LiMiC.

- I also found the paper: Design and Evaluation of Shared Memory CommunicationBenchmarks on Emerging Architectures using MVAPICH2
Is any of these designs incorporated in the MVAPICH2? I'm trying to look at the high level api mentioned in this paper(msg_enqueue/codemsg_dequeue) but I find nothing.

Best,
Zhiting
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