[GE users] MPICH2 startup methods

Reuti reuti at staff.uni-marburg.de
Fri Apr 29 12:59:01 BST 2005


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Hi Alan,

for now there is no check in my daemon-based startup, whether this chosen port 
is free on all the involved nodes for this job. But in a cluster with 
dual-headed nodes the chances are low (IMO), that any other process is just 
using this port. Also checking all nodes to have this calculated port free 
could lead to some race condition, where just another process accesses it. 
Maybe it would be an RFE for MPICH2, to negotiate the selected port on each 
node in both directions (like it is done in PVM).

Whether you will see a speed impact with the two startup methods depends on 
your job: if you are just starting one mpiexec, which will already cover the 
whole job, then there shouldn't be any noticable difference. If your job is 
starting many mpiexecs for any kind of iteration, then you would need the rsh 
calls for each daemonless mpiexec - then you may see a difference.

Cheers - Reuti

Quoting Alan Carriou <Alan.Carriou at jet.uk>:

> Hi
> 
> As we're going to use MPICH2 in our cluster, we'd like to know what 
> differences there are between the daemon-based and the daemon-less 
> startups. Any problem of performance, for instance, or risk of conflict 
> with the port settings concerning the daemon-based startup ?
> 
> Besides, as we already use MPICH1 to run MPI programs, will the choice 
> of the startup method make any difference when we will migrate ?
> 
> Thanks,
> Alan
> 
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