It is worth mentioning that there is a FAQ that describes the algorithm.
http://www.open-mpi.org/faq/?category=tcp#tcp-routability-1.3
Jeff Squyres wrote:
Sorry for the delay in replying; I kept starting to look into this and
then getting distracted by shiny objects. :-(
OMPI v1.3 actually has a fairly sophisticated TCP address/network
matching algorithm. The hostname resolution shouldn't really be the
issue; OMPI directly queries the kernel IP interfaces on each node
where it runs and publishes that to all other MPI processes. Then the
TCP network matching algorithm is used to select the "best" pairs to
connect to.
Per your diagram:
192.168.1.1 192.168.1.2
hubert ------------------------ fry
| \ / | 192.168.4.1
| \ / |
| \ / |
| \ / |
| / \ |
| / \ |
| / \ |
| / \ | 192.168.4.2
hermes ----------------------- leelas
I assume that the netmasks are all class C, right?
If so, I might ask you to run some diagnostic OMPI builds so that we
can see what the matching algorithm is doing on your machine...
On Apr 17, 2009, at 8:45 PM, Micha Feigin wrote:
I am having problems running openmpi 1.3 on my claster and I was
wondering if
anyone else is seeing this problem and/or can give hints on how to
solve it
As far as I understand the error, mpiexec resolves host names on the
master node
it is run on instead of an each host seperately. This works in an
environment where
each hostname resolves to the same address on each host (cluster
connected via a
switch) but fails where it resolves to different addresses (ring/star
setups for
example where each computer is connected directly to all/some of the
others)
I'm not 100% sure that this is the problem as I'm seeing success on a
single
case where this should probably fail but it is my best bet from the
error message.
version 1.2.8 worked fine for the same simple program (a simple
hellow world that
just comunicated the computer name for each process)
An example output:
mpiexec is run on the master node hubert and is set to run the
processes on two nodes
fry and leela. As is understood from the error messages leela tries
to connect to
fry on address 192.168.1.2 which is it's address on hubert but not
leela (where it
is 192.168.4.1)
This is a four node claster all interconnected
192.168.1.1 192.168.1.2
hubert ------------------------ fry
| \ / | 192.168.4.1
| \ / |
| \ / |
| \ / |
| / \ |
| / \ |
| / \ |
| / \ | 192.168.4.2
hermes ----------------------- leelas
=================================================================
mpiexec -np 8 -H fry,leela test_mpi
Hello MPI from the server process of 8 on fry!
[[36620,1],1][../../../../../../ompi/mca/btl/tcp/btl_tcp_endpoint.c:589:mca_btl_tcp_endpoint_start_connect]
from leela to: fry Unable to connect to the peer 192.168.1.2 on port
154: Network is unreachable
[[36620,1],3][../../../../../../ompi/mca/btl/tcp/btl_tcp_endpoint.c:589:mca_btl_tcp_endpoint_start_connect]
from leela to: fry Unable to connect to the peer 192.168.1.2 on port
154: Network is unreachable
[[36620,1],7][../../../../../../ompi/mca/btl/tcp/btl_tcp_endpoint.c:589:mca_btl_tcp_endpoint_start_connect]
from leela to: fry Unable to connect to the peer 192.168.1.2 on port
154: Network is unreachable
[leela:4436] *** An error occurred in MPI_Send
[leela:4436] *** on communicator MPI_COMM_WORLD
[leela:4436] *** MPI_ERR_INTERN: internal error
[leela:4436] *** MPI_ERRORS_ARE_FATAL (your MPI job will now abort)
[[36620,1],5][../../../../../../ompi/mca/btl/tcp/btl_tcp_endpoint.c:589:mca_btl_tcp_endpoint_start_connect]
from leela to: fry Unable to connect to the peer 192.168.1.2 on port
154: Network is unreachable
--------------------------------------------------------------------------
mpiexec has exited due to process rank 1 with PID 4433 on
node leela exiting without calling "finalize". This may
have caused other processes in the application to be
terminated by signals sent by mpiexec (as reported here).
--------------------------------------------------------------------------
[hubert:11312] 3 more processes have sent help message
help-mpi-errors.txt / mpi_errors_are_fatal
[hubert:11312] Set MCA parameter "orte_base_help_aggregate" to 0 to
see all help / error messages
=================================================================
This seems to be a directional issue as running the program -H
fry,leela failes
where -H leela,fry works, same behaviour for all senarious except
those that include
the master node (hubert) where it resolves the external ip (from an
external dns) instead
of the internal ip (from the hosts file). thus one direction fails
(no external connection
at the moment for all but the master) and the other causes a lockup
I hope that the explenation is not too convoluted
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