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From: Maestas, Christopher Daniel (cdmaest_at_[hidden])
Date: 2006-12-11 21:51:29

Hello Ralph,

This is great news! Thanks for doing this. I will try and get around
to it soon before the holiday break.

The allocation scheme always seems to get to me. From what you describe
that is how I would have seen it. As I've gotten to know osc mpiexec
through the years I think they like to do a first fit approach, but now
that I test it I think the feature needs more testing or I'm not testing
appropriately :-)

$ /apps/x86_64/system/mpiexec-0.82/bin/mpiexec -comm=none -npernode 2
grep HOSTNAME /etc/sysconfig/network
I guess I would wonder if it would be possible to switch from the method
what you suggest and also allow a "by-X-slot" style of launch where you
would see for npernode = X and N nodes:
 proc1 - node1
 proc2 - node1
 proc(X*1) - node1
 proc(X+1) - node2
 proc(X+2) - node2
 proc(X*2) - node2
 proc(N*X-(X-0)) - nodeN
 proc(N*X-(X-1)) - nodeN
 proc(X*N-1) - nodeN
 proc(X*N) - nodeN
I think that's how to best describe it.  Basically you load until there
are X processes on each node before moving to the next.  This may prove
to be more challenging, and I can understand if it would not be deemed
"worthy." :-)
> -----Original Message-----
> From: users-bounces_at_[hidden] 
> [mailto:users-bounces_at_[hidden]] On Behalf Of Ralph Castain
> Sent: Monday, December 11, 2006 5:41 PM
> To: Open MPI Users
> Subject: Re: [OMPI users] Pernode request
> Hi Chris
> Okay, we have modified the pernode behavior as you requested 
> (on the trunk
> as of r12821)- give it a shot and see if that does it. I have 
> not yet added
> the npernode option, but hope to get that soon.
> I have a question for you about the npernode option. I am 
> assuming that you
> want n procs/node, but that you want it mapped by NODE. For 
> example, proc 0
> goes on the first node, proc 1 goes on the second node, etc. 
> until I get one
> on each node; then I wrap back to the beginning and do this 
> again until I
> get the specified number of procs on each node.
> Correct?
> Ralph
> >Ralph,
> >I agree with what you stated in points 1-4. That is what we 
> are looking
> >for.
> >I understand your point now about the non-MPI users too. :-)
> >
> >Thanks,
> >-cdm
> >>-----Original Message-----
> >>From: users-bounces_at_[hidden] 
> [mailto:users-bounces_at_[hidden]] On
> >>Behalf Of Ralph Castain
> >>Sent: Wednesday, November 29, 2006 8:01 AM
> >>To: Open MPI Users
> >>Subject: Re: [OMPI users] Pernode request
> >>
> >>Hi Chris
> >>
> >>Thanks for the patience and the clarification - much appreciated. In
> >>fact, I have someone that needs to learn more about the 
> code base, so I
> >>think I will assign this to him. At the least, he will have 
> to learn a
> >>lot more about the mapper!
> >>
> >>I have no problem with modifying the pernode behavior to 
> deal with the
> >>case of someone specifying -np as you describe. It would be 
> relatively
> >>easy to check. As I understand it, you want the behavior to be:
> >>
> >>1. if no -np is specified, launch one proc/node across 
> entire allocation
> >>
> >>2. if -np n is specified AND n is less than the number of allocated
> >>nodes, then launch one proc/node up to the specified 
> number. Of course,
> >>this is identical to just doing -np n -bynode, but that's 
> immaterial.
> >>;-)
> >>
> >>3. if -np n is specified AND n is greater than the number 
> of allocated
> >>nodes, error message and exit
> >>
> >>4. add a -npernode n option that launches n procs/node, 
> subject to the
> >>same tests above.
> >>
> >>Can you confirm?
> >>
> >>Finally, I think you misunderstood my comment about the MPI 
> folks. Our
> >>non-MPI users couldn't care less about commonality of command line
> >>arguments across MPI implementations. Hence, I leave issues 
> in that area
> >>to the MPI members of the team - they are the ones that 
> decide how to
> >>deal with the myriad of different option syntaxes in the 
> MPI community.
> >>
> >>Gives me too much of a headache! :-)
> >>
> >>Ralph 
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