search

Warwick-Plasma / epoch

Particle-in-cell code for plasma physics simulations
https://epochpic.github.io
GNU General Public License v3.0
184 stars 58 forks source link

mpirun -np 80 #719

Closed Garnet5867 closed 2 weeks ago

Garnet5867 commented 1 month ago

Dear Author,

My question is: When running EPOCH, we initially used 80 threads, but after reinstalling EPOCH, it can only detect 40 threads. Could this be a compilation issue? No errors occurred during the compilation process.

Best regards.

Status-Mirror commented 1 month ago

I think an EPOCH domain needs a minimum of 5 cells. If your simulation has fewer than 400 cells, it won't be able to run with 80 threads.

Hope this helps, Stuart

Garnet5867 commented 1 month ago

Dear Professor, Hello! We have resolved the issue and discovered that it was caused by an outdated version of the MPICH parallel library, which led to recognition problems. During testing, we noticed that OpenMPI could only recognize 40 threads. We’re not sure why this is happening and would greatly appreciate any insights you might have.Thank you for your assistance!

Status-Mirror commented 2 weeks ago

Hi @Garnet5867,

I'm happy you resolved the issue! I've noticed similar behaviour to what you describe before on some systems, and I think it's related to hyperthreading - where the system splits each core into 2, allowing MPI to run with effectively double the number of physical cores. Maybe this is something to look into for a better understanding.

Cheers, Stuart