On May 5, 2005, at 5:54 AM, Jiri Barnat wrote:
> 1) I would like to run a single computation that performs
> simultaneously on computers in two different clusters. Unfortunately,
> computers in both clusters are attached to local networks only, so
> they don't have publically available IP addresses. Each cluster has an
> access point instead, which is a computer that has two network devices
> and two IP addresses, one local and one public. Is it possible to run
> such a computation with LAM/MPI impirun and impi_server?
It should be, yes. Note that there is currently a bug with regards to
IMPI startup in LAM 7.1.1 (fixing it is one of the last things we're
waiting for before releasing 7.1.2).
> 2) I tried to run computation through an impi_server only on those 2
> cluster access points mentioned above. However, connection didn't
> succeed because local IP addresses were used instead of the public
> ones. Is there any way, like environment variable or hidden
> impirun/mpirun parameter, that will allow to say which IP address
> should be anounced through impi_server to the others?
In terms of the server, you should be able to use any IP address on the
client that resolves to the node where the server is running. That is,
even if the server reports a.b.c.d as its IP address on its stdout
(e.g., if a.b.c.d turns out to be the private address), if a client
that can only connect to that node via the public address w.x.y.z, the
client should be able to use the public address as the argument to
mpirun's -client parameter and it should work.
The problem will come in the next step, however. The IMPI clients will
upload their contact information to the IMPI server -- if they upload
the wrong IP address (e.g., if they upload their private addresses),
peer clients won't be able to connect.
There is an environment variable that allows you to effectively
override the local hostname that the client will use to determine its
IP address. If you set the environment variable IMPI_HOST_NAME before
running the local client, this is the name that the client will resolve
to the IP address that is sent to the server. There is brief mention
of this environment variable in the LAM/MPI User's Guide in section
12.6 -- you might want to check this out.
--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
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