[Beowulf] problem : mpi dynamic scheduling ??

Mark Hahn hahn at physics.mcmaster.ca
Tue Jul 5 13:04:03 EDT 2005


> i m using mpiJava and i need to know ,Do MPI 0ffers Api's / Functions for
> dynamic scheduling , Process migration , Load and balancing?? . 

not generally, and I think there are good reasons, not just laziness.

to make any large, tightly-coupled application run efficiently, each proc
needs to avoid being preempted.  that means that you really can't do any
load-balancing, since you have to set aside a whole cpu for a proc, and hope
that the kernel and random daemons don't interfere too much.  (indeed, there
are systems which try to micro-kernel-ize the environment.  it's also
traditional to gang-schedule, so that if you really need to run a daemon, you
do it on all nodes at once.)

in other words, large-tight apps are incompatible with meaningful
load-balancing.  

not all the world consists of large, tightly coupled MPI applications, of
course.  but I'm pretty convinced that for looser applications, especially in
the presence of dynamic parallelism, and migration, I'd try to build a sort
of peer-to-peer version of Linda, rather than use MPI.

regards, mark hahn.

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