Ralph Castain wrote:
Hi Pak
I'm afraid I don't fully understand your question, so forgive me if I
don't seem to address the problem adequately. As I understand it, you
are asking about the scenario where someone wants to execute multiple
calls of mpirun, with the applications executing on the same set of
nodes. Your question is: why does OpenRTE spawn a new daemon (orted) on
the node each time we execute mpirun - why doesn't it just use the
existing one to launch the new application process(es)?
Assuming I have the question right, the short answers are "may not be
permitted" and "not yet implemented". :-)
yes, Ralph, that is precisely the question. good thing that you've
figured that out :)
First, the fact that an orted already exists on a node is not sufficient
to allow us to use it again for another application. The orted must be
persistent or else we do not allow a new application to re-use it. This
is required because the existing orted will go away when its original
application is done executing - if we use it as our parent to launch
another child, then the new application process will "die" when the
original one completes. Obviously, that isn't desirable.
okay. I used to think that if orted is able to stay and fork other
processes, but I didn't realize orted will go away once the parent
process finishes.
Second, even though you can launch persistent orteds today, none of the
current components in the resource management subsystems actually know
how to use them yet. This is something we planned to implement in the
future, but there simply hasn't been time to do so yet.
So the bottom line is that there really is no way around the need to
launch a new orted on each node every time the user issues an mpirun
command.
I hope that answers your question. If not, please don't hesitate to let
me know.
Thanks for pointing out these issues. I was hoping something I didn't
know may solve my problem. I guess there may not be a good workaround
for this limitation due to SGE slots. We could try to track and set some
top limit for the number of times that qrsh can exec, before the spawn
program uses up all the available SGE slots and errors out.
Ralph
Pak Lui wrote:
Hi,
When I run a spawn program over rsh/ssh, I notice that each time the
child program gets spawned, it will need to establish a new rsh/ssh
connection to the remote node to launch orted on that node, even the
parent executable and the orted are running on that node.
So I wonder if there is any way that we can use the parent orted to
launch the child program if they happen to be on the same node?
I try to compare to the spawn program to the scenario where I run
multiple executables in one mpirun command. For this run, I only
establish one connection to the remote node only, and both executables
shared the same remote connection.
% ./mpirun -np 2 -host burl-ct-v440-5 -prefix `pwd`/.. sleep 12 : -np 2
sleep 10
Password:
15015 /workspace/paklui/ompi/trunk/builds/sparc32-g/bin/../bin/orted
--bootprox
15017 sleep 12
15019 sleep 12
15021 sleep 10
15023 sleep 10
The reason that I want to find out if it is possible for orted to
launch child executable(s) without having to establish a new
connection, is because the number of times that I can run 'qrsh' in
SGE (or N1GE) is actually depended on the number of slots that the
user initially allocated. That the slot number corresponds to the
number of CPUs on a node. Each slot allows one 'qrsh' connection.
The issue is when I try to run a spawn job on a single node, or a
cluster of many 1-cpu nodes under SGE. The number of times that the
program can spawn is limited by 'qrsh', that it forbids the child
program to connect to the same node where the parent executable's
orted might be already running there.
I am curious to see if I can find some solution to the problem here. I
am also looking to see if there are some tricks in SGE to get around
this issue, but workaround I can see aren't pretty though. So I
welcome your questions, comments or suggestions on this.
--
Thanks,
- Pak Lui
pak....@sun.com
