problem about use mpiexec

[Pete Wyckoff]

ylqnew2000 at 263.sina.com said:
>     And today,i installed mpiexec-0.70 successfully,but when i use it
>     ,there still seemed some problems,just like the follows:
>     I use mpiexec just like mpirun (mpiexec -np 2 executalbe),but it
>     pop up an error which says that there are only one processor,and
>     when i use -np 1,it run the executable successfully), but i don't
>     know how to make mpiexec to run multi_processor executable?

You must have asked PBS for only one processor---mpiexec can only use
what it has been allocated by PBS.  Try something like:

    qsub -l nodes=1:ppn=2

if you want to use both processors on the node.

>    Another very important question is: People use mpiexec because they
>    don't need to do the rcp operation any more.Because it is done auto
>    by mpiexec,but in the directory of mpiexec-0.70,i don't find where
>    to set the machine name(you know,if you use mpirun,there are a file
>    named machine.LINUX,in which there are the node's name which can be
>    used while you apply for multi_nodes,but in mpiexec, i can not find
>    these kind of file,...?? so,where to set to make mpiexec use
>    multi_nodes, where to set their name?

It's not the rcp operation we're avoiding, it's the rsh used by mpich to
startup the code.

Read about PBS to see how to ask for multiple nodes.  mpiexec gets the
names of the nodes from PBS at each and every run.  Try

    qsub -I -l nodes=4:ppn=2
    ...
    mpiexec -comm=none hostname

to see how the allocation granted by PBS matches the nodes on which
mpiexec starts the codes.

		-- Pete