Am 02.12.2019 um 22:14 schrieb Mccall, Kurt E. (MSFC-EV41) via discuss <[email protected]>:

My application uses mainly inter-communicators rather than intra-communicators for fault tolerance. A particular process might have 20 inter-communicators active at one time. I’m receiving the warning

[[email protected]] WARNING: too many ssh connections to n009.cluster.com; waiting 6 seconds

What is the cause of this? I have several guesses:

1) MPICH has an internal limit on the number of connections 2) I’m bumping up against a Linux limit on the number of connections 3) Non-blocking communication using MPI_Isend() creates a temporary ssh connection (not likely)

4) Firewall or PAM settings on the target prevent to many logins in a certain timeframe. Are you using a queuing system and have the chance to skip SSH and startup MPICH by the queuing system? -- Reuti

The other question is, what are the consequences of “waiting 6 seconds”? Are some non-blocking messages dropped?

I’m using MPICH 3.3.2, CentOS 3.10 and the Portland Group compiler pgc++ 19.5.0.

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