[LESlie]

Dear Foamers,

After searching for a while on the forum about the performance of parallelization I decided to open this new thread to be able to specify better my problem.

I am doing a speed-up test of an industrial application of two phase flow. The mesh is 64 million cells, and the solver is compressibleInterFoam. Each node of the cluster contains 2 eight cores CPU Sandy Bridge clocked at 2.7 GHz (AVX), let 16 cores / node. Each node has 64 GB of memory, let 4 GB / core.

Respecting the rule of thumb of 50 k cells/processor, I have carried out the performance study on 1024 (62,500 cells/processor), 512 and 256 processors respectively using the scotch decomposition method. The real physical time to compute a same simulated period is 1.35, 1.035, and 1 (normalized by the physical time of using 256 processors) respectively, thus leaving the 1024 the least efficient configuration and the 256 the most efficient.

Any help or suggestion will be very appreciated.