I found the manual pages for mpirun and orte_hosts, which have a pretty thorough description of these features. Let me know if there's anything else I should check out.
My quick impression is that this will meet at least 90% of user needs out of the box as most (all?) users will run with number of job processors that divides into PPN or is a multiple of PPN. The docs imply that the relative indexing is relative to nodes as opposed to slots. If so, it's easy to cover my cases 1 and 2 with modulo arithmetic right on the command line, but the edge case 3 might require creation of host files or a maps file, specifying specific nodes and slots. I'm still trying to fully wrap my head around the way the scheduling works and the nodes/slots distinction, so have to think on this. For example, in a PBS/Torque environment, I guess each processor gets an entry as a "node" in the $PBS_NODEFILE, so maybe this won't be an issue for many of our machines. Another potential gotcha is the scheduler driving my M scheduler processes ideally runs asynchronously (since not all compute jobs take equal time as parameters vary), so initially jobs 0--M could be on resource blocks 0--M in order, but if job 2 finishes first, I'd want to put job M+1 on block 2. So I might end up needing some glue code anyway for the dynamic scheduling case. What's in ORTE today will likely work great in the static scheduling case. Brian ________________________________ From: users-boun...@open-mpi.org [mailto:users-boun...@open-mpi.org] On Behalf Of Ralph Castain Sent: Thursday, July 30, 2009 2:08 PM To: Open MPI Users Subject: Re: [OMPI users] Multiple mpiexec's within a job (schedule within a scheduled machinefile/job allocation) Let me know how it goes, if you don't mind. It would be nice to know if we actually met your needs, or if a tweak might help make it easier. Thanks Ralph On Jul 30, 2009, at 1:36 PM, Adams, Brian M wrote: Thanks Ralph, I wasn't aware of the relative indexing or sequential mapper capabilities. I will check those out and report back if I still have a feature request. -- Brian ________________________________ From: users-boun...@open-mpi.org [mailto:users-boun...@open-mpi.org] On Behalf Of Ralph Castain Sent: Thursday, July 30, 2009 12:26 PM To: Open MPI Users Subject: Re: [OMPI users] Multiple mpiexec's within a job (schedule within a scheduled machinefile/job allocation) On Jul 30, 2009, at 11:49 AM, Adams, Brian M wrote: Apologies if I'm being confusing; I'm probably trying to get at atypical use cases. M and N need not correspond to the number of nodes/ppn nor ppn/nodes available. By node vs. slot doesn't much matter, as long as in the end I don't oversubscribe any node. By slot might be good for efficiency in some apps, but I can't make a general case for it. I think what you proposed offers some help in the case where N is an integer multiple of the number of available nodes, but perhaps not in other cases. I must be missing something here, so instead of being fully general, perhaps consider a specific case. Suppose we have 4 nodes, 8 ppn (32 slots is I think the ompi language). I might want to schedule, for example 1. M=2 simultaneous N=16 processor jobs: Here I believe what you suggested will work since N is a multiple of the available number of nodes. I could use either npernode 4 or just bynode and I think get the same result: an even distribution of tasks. (similar applies to, e.g., 8x4, 4x8) Yes, agreed 2. M=16 simultaneous N=2 processor jobs: it seems if I use bynode or npernode, I would end up with 16 processes on each of the first two nodes (similar applies to, e.g., 32x1 or 10x3). Scheduling many small jobs is a common problem for us. 3. M=3 simultaneous, N=10 processor jobs: I think we'd end up with this distribution (where A-D are nodes and 0-2 jobs) A 0 0 0 1 1 1 2 2 2 B 0 0 0 1 1 1 2 2 2 C 0 0 1 1 2 2 D 0 0 1 1 2 2 where A and B are over-subscribed and there are more than the two unused slots I'd expect in the whole allocation. Again, I can manage all these via a script that partitions the machine files, just wondering which scenarios OpenMPI can manage. Have you looked at the relative indexing in 1.3.3? You could specify any of these in relative index terms, and have one "hostfile" that would support 16x2 operations. This would work then for any allocation. Your launch script could even just do it, something like this: mpirun -n 2 -host +n0:1,+n1:1 app mpirun -n 2 -host +n0:2,+n1:2 app etc. Obviously, you could compute the relative indexing and just stick it in as required. Likewise, you could use the new "seq" (sequential) mapper to achieve any desired layout, again utilizing relative indexing to avoid having to create a special hostfile for each run. Note that in all cases, you can specify a -n N that will tell OMPI to only execute N processes, regardless of what is in the sequential mapper file or -host. If none of those work well, please let me know. I'm happy to create the required capability as I'm sure LANL will use it too (know of several similar cases here, but the current options seem okay for them). Thanks! Brian -----Original Message----- From: users-boun...@open-mpi.org<mailto:users-boun...@open-mpi.org> [mailto:users-boun...@open-mpi.org] On Behalf Of Ralph Castain Sent: Wednesday, July 29, 2009 4:19 PM To: Open MPI Users Subject: Re: [OMPI users] Multiple mpiexec's within a job (schedule within a scheduled machinefile/job allocation) Oh my - that does take me back a long way! :-) Do you need these processes to be mapped byslot (i.e., do you care if the process ranks are sharing nodes)? If not, why not add "-bynode" to your cmd line? Alternatively, given the mapping you want, just do mpirun -npernode 1 application.exe This would launch one copy on each of your N nodes. So if you fork M times, you'll wind up with the exact pattern you wanted. And, as each one exits, you could immediately launch a replacement without worrying about oversubscription. Does that help? Ralph PS. we dropped that "persistent" operation - caused way too many problems with cleanup and other things. :-) On Jul 29, 2009, at 3:46 PM, Adams, Brian M wrote: Hi Ralph (all), I'm resurrecting this 2006 thread for a status check. The new 1.3.x machinefile behavior is great (thanks!) -- I can use machinefiles to manage multiple simultaneous mpiruns within a single torque allocation (where the hosts are a subset of $PBS_NODEFILE). However, this requires some careful management of machinefiles. I'm curious if OpenMPI now directly supports the behavior I need, described in general in the quote below. Specifically, given a single PBS/Torque allocation of M*N processors, I will run a serial program that will fork M times. Each of the M forked processes calls 'mpirun -np N application.exe' and blocks until completion. This seems akin to the case you described of "mpiruns executed in separate windows/prompts." What I'd like to see is the M processes "tiled" across the available slots, so all M*N processors are used. What I see instead appears at face value to be the first N resources being oversubscribed M times. Also, when one of the forked processes returns, I'd like to be able to spawn another and have its mpirun schedule on the resources freed by the previous one that exited. Is any of this possible? I tried starting an orted (1.3.3, roughly as you suggested below), but got this error: orted --daemonize [gy8:25871] [[INVALID],INVALID] ORTE_ERROR_LOG: Not found in file runtime/orte_init.c at line 125 ---------------------------------------------------------------------- ---- It looks like orte_init failed for some reason; your parallel process is likely to abort. There are many reasons that a parallel process can fail during orte_init; some of which are due to configuration or environment problems. This failure appears to be an internal failure; here's some additional information (which may only be relevant to an Open MPI developer): orte_ess_base_select failed --> Returned value Not found (-13) instead of ORTE_SUCCESS ---------------------------------------------------------------------- ---- [gy8:25871] [[INVALID],INVALID] ORTE_ERROR_LOG: Not found in file orted/orted_main.c at line 323 I spared the debugging info as I'm not even sure this is a correct invocation... Thanks for any suggestions you can offer! Brian ---------- Brian M. Adams, PhD (bria...@sandia.gov<mailto:bria...@sandia.gov>) Optimization and Uncertainty Quantification Sandia National Laboratories, Albuquerque, NM http://www.sandia.gov/~briadam From: Ralph Castain (rhc_at_[hidden]) List-Post: users@lists.open-mpi.org Date: 2006-12-12 00:46:59 Hi Chris Some of this is doable with today's code....and one of these behaviors is not. :-( Open MPI/OpenRTE can be run in "persistent" mode - this allows multiple jobs to share the same allocation. This works much as you describe (syntax is slightly different, of course!) - the first mpirun will map using whatever mode was requested, then the next mpirun will map starting from where the first one left off. I *believe* you can run each mpirun in the background. However, I don't know if this has really been tested enough to support such a claim. All testing that I know about to-date has executed mpirun in the foreground - thus, your example would execute sequentially instead of in parallel. I know people have tested multiple mpirun's operating in parallel within a single allocation (i.e., persistent mode) where the mpiruns are executed in separate windows/prompts. So I suspect you could do something like you describe - just haven't personally verified it. Where we definitely differ is that Open MPI/RTE will *not* block until resources are freed up from the prior mpiruns. Instead, we will attempt to execute each mpirun immediately - and will error out the one(s) that try to execute without sufficient resources. I imagine we could provide the kind of "flow control" you describe, but I'm not sure when that might happen. I am (in my copious free time...haha) working on an "orteboot" program that will startup a virtual machine to make the persistent mode of operation a little easier. For now, though, you can do it by: 1. starting up the "server" using the following command: orted --seed --persistent --scope public [--universe foo] 2. do your mpirun commands. They will automagically find the "server" and connect to it. If you specified a universe name when starting the server, then you must specify the same universe name on your mpirun commands. When you are done, you will have to (unfortunately) manually "kill" the server and remove its session directory. I have a program called "ortehalt" in the trunk that will do this cleanly for you, but it isn't yet in the release distributions. You are welcome to use it, though, if you are working with the trunk - I can't promise it is bulletproof yet, but it seems to be working. Ralph On 12/11/06 8:07 PM, "Maestas, Christopher Daniel" <cdmaest_at_[hidden]> wrote: Hello, Sometimes we have users that like to do from within a single job (think schedule within an job scheduler allocation): "mpiexec -n X myprog" "mpiexec -n Y myprog2" Does mpiexec within Open MPI keep track of the node list it is using if it binds to a particular scheduler? For example with 4 nodes (2ppn SMP): "mpiexec -n 2 myprog" "mpiexec -n 2 myprog2" "mpiexec -n 1 myprog3" And assume this is by-slot allocation we would have the following allocation: node1 - processor1 - myprog - processor2 - myprog node2 - processor1 - myprog2 - processor2 - myprog2 And for a by-node allocation: node1 - processor1 - myprog - processor2 - myprog2 node2 - processor1 - myprog - processor2 - myprog2 I think this is possible using ssh cause it shouldn't really matter how many times it spawns, but with something like torque it would get restricted to a max process launch of 4. We would want the third mpiexec to block processes and eventually be run on the first available node allocation that frees up from myprog or myprog2 .... For example for torque, we had to add the following to osc mpiexec: --- Finally, since only one mpiexec can be the master at a time, if your code setup requires that mpiexec exit to get a result, you can start a "dummy" mpiexec first in your batch job: mpiexec -server It runs no tasks itself but handles the connections of other transient mpiexec clients. It will shut down cleanly when the batch job exits or you may kill the server explicitly. If the server is killed with SIGTERM (or HUP or INT), it will exit with a status of zero if there were no clients connected at the time. If there were still clients using the server, the server will kill all their tasks, disconnect from the clients, and exit with status 1. --- So a user ran: mpiexec -server mpiexec -n 2 myprog mpiexec -n 2 myprog2 And the server kept track of the allocation ... I would think that the orted could do this? Sorry if this sounds confusing ... But I'm sure it will clear up with any further responses I make. :-) -cdm _______________________________________________ users mailing list users_at_[hidden] http://www.open-mpi.org/mailman/listinfo.cgi/users _______________________________________________ users mailing list us...@open-mpi.org<mailto:us...@open-mpi.org> http://www.open-mpi.org/mailman/listinfo.cgi/users _______________________________________________ users mailing list us...@open-mpi.org<mailto:us...@open-mpi.org> http://www.open-mpi.org/mailman/listinfo.cgi/users _______________________________________________ users mailing list us...@open-mpi.org<mailto:us...@open-mpi.org> http://www.open-mpi.org/mailman/listinfo.cgi/users _______________________________________________ users mailing list us...@open-mpi.org<mailto:us...@open-mpi.org> http://www.open-mpi.org/mailman/listinfo.cgi/users
