[SOLVED] MD simulation speed with respect to number of CPUs

[kevenalkhoury]

I am currently running MD simulations on a HPC.
Some simulations are running faster for a lower number of CPUs. In other words, sometimes I run the same simulation on 10 and 20 CPUs, and the simulation running on the 10 CPUs runs faster.
Can anyone explain how is that possible?
Thank you.

 

[kanewolf]

How many physical CPU cores are there? Is hyperthreading enabled on the host?

It could be a memory limitation, or a hyperthreading problem or code that doesn't scale well. Anything is possible. Without WAY more infor on the physical host, there is no easy answer.