On Jun 29, 2009, at 2:19 AM, vipin kumar wrote:
Q. Since I am using TCP/Ethernet I guess that MPI uses SSH/RSH to
communicate between peers.
Ans. May be you are right. I don't know exactly how peers
communicate in MPI environment, but I can say for sure that OpenMPI
uses rsh/ssh as one of the available launchers.
Open MPI uses two different mechanisms for launching individual MPI
processes vs. MPI communications. rsh/ssh is one of the options that
Open MPI can use for launching MPI processes, but we don't keep those
channels open and don't use them for MPI communications. Individual,
new TCP sockets are opened for MPI_SEND / MPI_RECV (etc.) traffic.
These sockets are not encrypted (like ssh connections would be).
Q. And for that, each peer should have the copy of the application
right?
Ans. Absolutely correct. But If you don't want to copy binaries
manually you should use "--preload-binary" option. OpenMPI will copy
the executables in remote nodes before launching processes, and will
delete when job gets done.
It is almost always good to use latest version. "--preload-binary"
option may be absent in old versions.
It is new in the 1.3 series; it did not exist in the 1.2 series.
--
Jeff Squyres
Cisco Systems
