Hi, On 12/1/21 1:31 PM, Joachim Protze via discuss wrote:

I think, calling MPI_Comm_free from the garbage collector in random ordering is not valid MPI code, since this function is a collective operation. The non-normative advice to implementers reads:

Though collective, it is anticipated that this operation will normally be implemented to be local, though a debugging version of an MPI library might choose to synchronize.

just an additional thought: for MPI_Win_free, ordering also matters, _and_ it must be called for each and every corresponding window creation before calling MPI_Finalize. Regards, Thomas