[datTommyGuy]

Hello,
I'm meshing a more-or-less cylindrical geometry (screenshot attached below, flow through a duct) with sHM. I used a simple (2 2 2) decomposition in decomposeParDict ((2 2 1) for 4 threads). I'm running the case in this order:


blockMesh
surfaceFeatures

decomposePar
mpirun -np 8 snappyHexMesh -overwrite -parallel


However, the more cores I use, the slower snappyHexMesh runs. Just adding new boundary patches takes too long to let it finish the job.



I'm using Ubuntu 16.04 LTS on Windows 10. The processor is a 4-core (8 threads) i7-7700HQ. When using 8 threads, the CPU usage jumps to 100%, while with 4 it stays at about 60%, so the decomposition itself seems to be working.


What may be the cause of such behaviour? I'll gladly provide more details as needed.