[Users] Using "mpirun -np 2" make the program much slower ?

[赵志超]

Hello, everyone,

I am a beginner in Institute of High Energy Physics, China.

I am using ubuntu16.04 and my machine has two cpus:

       Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GHz X2

I am trying to repeat "Gallery: Binary, inspiraling neutron stars forming a
hypermassive neutron star" in
http://einsteintoolkit.org/gallery/bns/index.html. I am using the par file
and thornlist.th provided in the webpage.

However, I found it runs slowly when I run with "mpirun -np 2 ./Cactus_sim
nsns.par". It needs about 600s per iteration. All cpu's usage are 100%.

Then I try to directly run with command "./Cactus_sim nsns.par", then it
needs about 13s per iteration. All cpu's usage are 100%.

And then, I try to run with "numactl --cpunodebind=0 --preferred=0
./cactus_sim nsns.par", It only needs 2.5s per iteration. And just half cpu
( 28 of 56 )'s usage are 100%.

I wonder is there some error? I think it should be faster when mpirun are
used.

Yours,
ZhiChao.
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