Core allocation

[Joe-Fitzy]

Hi,

May be a silly question but I'm still very new to FDS.

If I'm running 2 simulations on the same PC how do I know they're allocated to different cores?

Currently i just use the "fds_local -p 4 FDSname.FDS"

My PC has 12 cores and i have been trying to use 4 cores each to run 3 sims at a time over the weekend.

Any confirmation would be great thanks.

[nsarifds]

To speed up your simulation time you can use both cores (MPI processes), that split the problem into different parts (each part gets a core), as well as threads, that use multiple logical processors to work simultaneously on each part of the problem. Cores can work as threads but logical processors cannot work as mpi processes. That means the amount of splitting of your problem you can do is limited by your cores.

By going to "Task Manager" and then "Performance", "CPU", you can see the number of cores and logical processors. If you have for example 12 cores and 24 logical processors, that means you can use 2 threads per core (2 threads/core12 cores = 24 logical processors). However using 100% of your CPU will probably negatively impact your sim time. So you would opt for 1 thread/core (112cores=12<24) or 2 threads/core for only 2 of your sims to try and keep threadscores<logical processors. (28cores+1*4cores=20<24)

If your sims are 1 mesh each , then you need OpenMP Enabled, with 4 threads enabled, N_THREADS=4/ (3 sims*4 threads = 12 cores, because cores can work as threads). If your sims have more than 1 mesh, then you need to assign your meshes to different MPI processes (cores) by writing ,MPI_PROCESS=0/ for the first core, =1/ for the second, etc. For example, if 12 meshes would be split into 4 cores then 3 meshes would share the same core and the same line MPI_PROCESS=x/.

Try to keep the number of cells/mesh equal and dont go above 4 threads/process to optimize your speed!

[Joe-Fitzy]

so say i had 3 seperate FDS running on one pc/server would i allocate -p 4 to all of the sims. However, in the code allocate the first sim as Mpi_process=0 to mpi_process=3 across its meshes. then on the next FDS i would allocate Mpi_process=4 to mpi_process=7across its meshes?

[nsarifds]

Now I understand exactly what your question was. I would suggest naming all processes from 0-3. Go to "Start" "Resource Monitor" "CPU" and see what happens to your core's usage starting from one sim and adding the rest.

[nsarifds]

You would see the number of MPI processes of each sim here: