mpiexec

[Pete Wyckoff]

binarywish at hotmail.com wrote on Mon, 07 Feb 2005 12:07 -0500:
> OK guys, I am new to this mpiexec, so please help me as much as you can
> I just installed mpich2 on a linux cluster. I was used to the mpich1.2.6.
> Anyway, here is what i want to accomplish. Suppose I have a.out that needs 
> to
> run on 4 nodes, mach1, mach2, mach3, and mach4.
> I want the rank in the communicator however to be mapping to physical nodes
> as follows: (0->mach4) (1->mach3) (2->mach2) (3->mach1)
> assume i have a file "hosts" that contains
> mach1
> mach2
> mach3
> mach4
> 
> >From what i understood from mpich2 documentation, i have to first do
> mpd -n 4 -f hosts
> 
> then run mpiexec -n 4 a.out

Likely wrong mpiexec.  See
    http://www.osc.edu/~pw/mpiexec/index.html#toomany

> well, how does mpiexec map the physical nodes to logical rank is this case?
> does it assign logical ranks based on the host order as it appears in the 
> hosts
> file? If not, then How do i accomplish what i want?

If you are not using MPD, and you are sure you have the correct mpiexec,
and you run PBS on your cluster, the answer is no:  task order is fixed
as listed in $PBS_NODEFILE.  That can be fixed in the code if you are so
motivated.  See the archives for the thread "order of assign MPI_rank
to nodes" in Dec 2004.

		-- Pete