[MPICH] Stopping processors?

[Darius Buntinas]

One idea would be to have each worker process spawn a "computation" 
thread which actually does the computation.  The "main" thread of the 
process would issue a blocking receive waiting for a "done" message.

When a computation thread at some process finishes, it sends messages to 
the other processes and to itself.  When a main thread receives a done 
message, it checks whether it received the message from its own 
computation thread.  If so, it does a pthread_join() and reads the 
result, otherwise it does a pthread_cancel().

At this point the main thread can wait for a message to start the next 
computation.


If you have a lot of processes having one process send a done message to 
every other process isn't scalable.  You could optimize in that case by 
having the processes forward the message in a tree.

-d

Michaela Heyer wrote:
> Hi,
> I'm hoping someone can help me with this...
> Essentially I'm looking for a way to tell one or more processors to stop 
> whatever they are currently doing and move on to something else. The 
> situation is as follows: Let's say we have n processors all working on 
> different algorithms. I only really need the result of one of these 
> algorithms so whichever processor finishes first should tell all the other 
> ones to stop so they can all move on to the next problem. It's a bit like a 
> race...and speed is vital! (That's why I can't really wait for all processors 
> to finish their algorithms)
> At the moment I'm using MPI_Abort() to shutdown the whole process. This works 
> fine and does exactly what I need but the problem is that it is very very 
> slow as it shuts down and restarts all the processors. So what I'm looking 
> for is something like a "milder" version of MPI_Abort() i.e. stop everything 
> but don't shutdown the processors.
> I have been looking but can't find anything sutitable so I'm starting to think 
> that maybe it's impossible? It would be great if you could prove me wrong :-)
> Thanks,
> Michaela
>