Thunderhead Engineering Forum

Public Forum => PyroSim => Topic started by: roborob on September 04, 2019, 03:50:05 am

Title: disable MPI if simulating only with openPM
Post by: roborob on September 04, 2019, 03:50:05 am
Hi. I hope this is a simple question. I am new to FDS.

So a colleague of mine has left and has handed me some simulations that have already taken months and have months more to go. The meshes were not divided up, it is just one huge mesh. It is an eight core machine, with 1 MPI process and 6 openMP threads. I just turned off hyper-threading and restarted.

So as I understand it, there is no point in using MPI, so is there an advantage to disabling it (if that is possible)? and only use OpenPM.

To be honest, I am a bit confused, if I have 1 MPI process, does that mean that the simulation is running on just one core? As the PC has one core constantly at 100%. whilst the other cores, are jumping between 10 and ~90% (but all 7 cores, not just the other 5, also confusing) .  So I am not even sure if the OpenMP is using all 6 cores, or if MPI has forced it on to a single core.

Thanks, I hope that is clear,
Rob