Hi, I have some questions regarding technical details of MPI collective communication methods and broadcast:
- I want to understand when the number of receivers in a MPI_Bcast can be a problem slowing down the broadcast. There are a few implementations of MPI_Bcast. Consider that of a binary tree. In this case, the sender (root) transmits the common message to its two children and each them to two more and so on. Is it accurate to say that in each level of the tree all transmissions happen in parallel or only one transmission can be done from each node? To that end, is there a limit on the number of processes a process can broadcast to in parallel? - Since each MPI_Bcast is associated with a communicator is there a limit on the number of processes a communicator can have and if so what is it in Open MPI? Regards, Kostas
