1. MPI_THREAD_SINGLE: Only one thread will execute.
Does this really mean the process cannot have any other threads at all, even if they doen't deal with MPI at all?
I'm curious as to how this case affects the openmpi implementation?
Essentially, what is the difference between MPI_THREAD_SINGLE and MPI_THREAD_FUNNELED?
2. In my case, I'm interested in MPI_THREAD_SERIALIZED. However if it's available, I can use MPI_THREAD_FUNNELED.
What cmake flags do I need to enable to allow this mode?
3. Assume I assign only 1 thread in my program to deal with MPI. What is the difference between