I'm using OpenMPI 2.1.0 on RHEL 7, communicating between ranks via TCP I have a new cluster to install my application on with tightly-controlled firewalls. I can have them open up a range of TCP ports which MPI can communicate over. I thought I could force MPI to stick to a range of ports via "--mca oob_tcp_static_ports startPort-endPort" but this doesn't seem to be working; I still seem MPI opening up TCP ports outside of this range to communicate. I've also seen "--mca oob_tcp_dynamic_ports" on message boards; I'm not sure what the difference is between these two but this flag doesn't seem to do what I want either.
Is there a way to lock the TCP port range down? As a general rule of thumb, if I'm communicating between up to 50 instances on a 10 Gbps network moving at several painful spots in the chain hundreds of GBs of data around, how large should I make this port range (i.e. if Open MPI would normally open a bunch of ports on each machine to improve the network transfer speed, I don't want to slow it down by allowing it too narrow of a port range). Just need a rough order of magnitude - 10 ports, 100 ports, 1000 ports? Thanks! -Adam
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