If you have a batch system that can start the MPDs, you should
consider starting the MPI processes directly with the batch system
and providing a separate service to provide the startup information.
In MPICH2, the MPI implementation is separated from the process
management. The mpd system is simply an example process manager
(albeit one with many useful features). We didn't expect users to
use one existing parallel process management system to start another
one; instead, we expected that those existing systems would use the
PMI interface used in MPICH2 to directly start the MPI processes. I
know that you don't need MPD for MPICH2; I expect the same is true
for Intel MPI.
Bill
On Oct 4, 2006, at 11:31 AM, Bill Bryce wrote:
Hi Matt,
You pretty much diagnosed our problem correctly. After discussing
with
the customer and a few more engineers here we found that the python
code
was very slow at starting the ring. Seems to be a common problem with
MPD startup on other MPI implementations as well (I could be wrong
though). We also modified the recvTimeout since onsite engineers
suspected that would help as well. The final fix we are working on is
starting the MPD with the batch system and not relying on ssh - the
customer does not want a root MPD ring and wants one per job so the
batch system will do this for us.
Bill.
-----Original Message-----
From: M J Harvey [mailto:[EMAIL PROTECTED]
Sent: Wednesday, October 04, 2006 12:23 PM
To: Bill Bryce
Cc: [email protected]
Subject: Re: [Beowulf] Intel MPI 2.0 mpdboot and large clusters, slow
tostart up, sometimes not at all
Hello,
We are going through a similar experience at one of our customer
sites.
They are trying to run Intel MPI on more than 1,000 nodes. Are you
experiencing problems starting the MPD ring? We noticed it takes a
really long time especially when the node count is large. It also
just
doesn't work sometimes.
I've had similar problems with slow and unreliable startup of the
Intel
mpd ring. I noticed that before spawning the individual mpds, it
connects to each node and checks the version of the installed python
(function getversionpython() in mpdboot.py). On my cluster, at least,
this check was very slow (not to say pointless). Removing it
dramatically improved startup time - now it's merely slow.
Also, for jobs with large process counts, it's worth increasing
recvTimeout in mpirun from 20 seconds. This value governs the
amount of
time mpirun waits for the secondary mpi processes to be spawned by the
remote mpds and the default value is much too aggressive for large
jobs
started via ssh.
Kind Regards,
Matt
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