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Subject: [OMPI users] how to get mpirun to scale from 16 to 64 cores
From: Yuping Sun (yupingpaulasun_at_[hidden])
Date: 2014-06-16 18:19:08

Dear All: I bought a 64 core workstation and installed NASA fun3d with open mpi 1.6.5. Then I started to test run fun3d using 16, 32, 48 cores. However the performance of the fun3d run is bad. I got data below: the run command is (it is for 32 core as an example) mpiexec -np 32 --bysocket --bind-to-socket ~ysun/Codes/NASA/fun3d-12.3-66687/Mpi/FUN3D_90/nodet_mpi --time_timestep_loop --animation_freq -1 > screen.dump_bs30 CPUs     times    iterations    time/it 60    678s    30it        22.61s 48    702s    30it        23.40s 32    734s    30it        24.50s 16    894s    30it        29.80s You can see using 60 cores, to run 30 iteration, FUN3D will complete in 678 seconds, roughly 22.61 second per iteration. Using 16 cores, to run 30 iteration, FUN3D will complete in 894 seconds, roughly 29.8 seconds per iteration. the data above shows FUN3D run using mpirun does not scale at all! I used to run fun3d with mpirun on a 8 core WS, and it scales well. The same job to run on a linux cluster scales well. Would you all give me some advice to improve the performance loss when I increase the use of more cores, or how to run mpirun with proper options to get a linear scaling when using 16 to 32 to 48 cores? Thank you. Yuping