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

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.