Thank you both for your suggestions!
I measured ~20000 packets/sec are exchanged between the 2 nodes during program execution, i guess that's too much; ping reports ~0.2ms for small packets. I also tried a more demanding (Coupled Cluster) calculation; it didn't provide any speedup either, but this time the limiting factor was throughput rather than latency, as transfer rates were constantly >950MBit.
I have downloaded and compiled NWChem 6.6 with ARMCI_NETWORK=MPI-PR. When i run it (even a single task) i always get the following error:
[0] Received an Error in Communication: (1) there must be at least two ranks per node
application called MPI_Abort(comm=0x84000000, 1) - process 0
Perhaps i should open a new thread under Compiling NWChem.
Thanks again,
Kostas
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