Reply To: Multi GPUs Calculation

[Yuji]

Dear Adrian,

I appreciate kind your answer.
Let me check and give me time in order to understand it.

As to your answer (( 3) No, same as 1 and 2. From the user side there is no MPI-related code difference between CPU-only and (multi)GPU mode.) and, If you delete MPI API usage it will still work for single GPUs / CPUs, just not multiple of them. (referring to all MPI usage in OpenLB not just the logging in the cavity3d benchmark case)) if I want to use multiple GPUs, I need to write MPI wrapper functions like in examples/laminar/cavity3dBenchmark. Is it my understanding right?

This is because I am being confused. As to your answer of ” 3) No, same as 1 and 2. From the user side there is no MPI-related code difference between CPU-only and (multi)GPU mode.)”, I dont need to write MPI wrapper functions. If the “PARALLEL_MODE” sets MPI in config.mk, it works in Multiple GPUs even though MPI wrapper is not written in .cpp.
However, as to “If you delete MPI API usage it will still work for single GPUs / CPUs, just not multiple of them. (referring to all MPI usage in OpenLB not just the logging in the cavity3d benchmark case)”, I have to write MPI wrapper in .cpp.
Which are these answer right?
Sorry, I am being confused…