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 _______________________________________________ Beowulf mailing list, [email protected] To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
