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Subject: [OMPI users] OpenMPI collective algorithm selection
From: chandan basu (cbasu_at_[hidden])
Date: 2013-04-05 08:10:04


Hi,

I want to use OpenMPI dynamic collective algorithm selection using rules
file, e.g.

mpirun --mca coll_tuned_use_dynamic_rules 1
--mca_coll_tuned_dynamic_rules_file rules.txt ./myexe

I can see some examples in earlier discussions (given below). My question
is how do I know the ID for the different collectives. I do not see
coll_tuned.h
in the installation folder . Is there any command to find the ID of an
algorithm. I am particularly interested in Alltoallv. I have checked that
coll_tuned_alltoallv_algorithm 1 and coll_tuned_alltoallv_algorithm 2 has
lot of performance difference depending on data size and comm size. So I
think giving a rules file can improve the performance over a range of data
sizes and comm size. Any help in this regard will be appreciated.

With regards,

-Chandan
----------------------------------------
Dr. Chandan Basu
National Supercomputer Center
Linköping University
S-581 83 Linköping
email: cbasu_at_[hidden]
-----------------------------------------
>1 # num of collectives
>3 # ID = 3 Alltoall collective (ID in coll_tuned.h)
>2 # number of com sizes
>1 # comm size 1
>1 # number of msg sizes 1
>0 1 0 0 # for message size 0, linear 1, topo 0, 0 segmentation
>8 # comm size 8
>4 # number of msg sizes
>0 1 0 0 # for message size 0, linear 1, topo 0, 0 segmentation
>32768 2 0 0 # 32k, pairwise 2, no topo or segmentation
>262144 1 0 0 # 256k, use linear 1, no topo or segmentation
>524288 2 0 0 # message size 512k+, pairwise 2, topo 0, 0 segmentation
># end of first collective

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