On Jul 6, 2010, at 8:48 AM, Grzegorz Maj wrote: > Hi Ralph, > sorry for the late response, but I couldn't find free time to play > with this. Finally I've applied the patch you prepared. I've launched > my processes in the way you've described and I think it's working as > you expected. None of my processes runs the orted daemon and they can > perform MPI operations. Unfortunately I'm still hitting the 65 > processes issue :( > Maybe I'm doing something wrong. > I attach my source code. If anybody could have a look on this, I would > be grateful. > > When I run that code with clients_count <= 65 everything works fine: > all the processes create a common grid, exchange some information and > disconnect. > When I set clients_count > 65 the 66th process crashes on > MPI_Comm_connect (segmentation fault).
I didn't have time to check the code, but my guess is that you are still hitting some kind of file descriptor or other limit. Check to see what your limits are - usually "ulimit" will tell you. > > Another thing I would like to know is if it's normal that any of my > processes when calling MPI_Comm_connect or MPI_Comm_accept when the > other side is not ready, is eating up a full CPU available. Yes - the waiting process is polling in a tight loop waiting for the connection to be made. > > Any help would be appreciated, > Grzegorz Maj > > > 2010/4/24 Ralph Castain <r...@open-mpi.org>: >> Actually, OMPI is distributed with a daemon that does pretty much what you >> want. Checkout "man ompi-server". I originally wrote that code to support >> cross-application MPI publish/subscribe operations, but we can utilize it >> here too. Have to blame me for not making it more publicly known. >> The attached patch upgrades ompi-server and modifies the singleton startup >> to provide your desired support. This solution works in the following >> manner: >> 1. launch "ompi-server -report-uri <filename>". This starts a persistent >> daemon called "ompi-server" that acts as a rendezvous point for >> independently started applications. The problem with starting different >> applications and wanting them to MPI connect/accept lies in the need to have >> the applications find each other. If they can't discover contact info for >> the other app, then they can't wire up their interconnects. The >> "ompi-server" tool provides that rendezvous point. I don't like that >> comm_accept segfaulted - should have just error'd out. >> 2. set OMPI_MCA_orte_server=file:<filename>" in the environment where you >> will start your processes. This will allow your singleton processes to find >> the ompi-server. I automatically also set the envar to connect the MPI >> publish/subscribe system for you. >> 3. run your processes. As they think they are singletons, they will detect >> the presence of the above envar and automatically connect themselves to the >> "ompi-server" daemon. This provides each process with the ability to perform >> any MPI-2 operation. >> I tested this on my machines and it worked, so hopefully it will meet your >> needs. You only need to run one "ompi-server" period, so long as you locate >> it where all of the processes can find the contact file and can open a TCP >> socket to the daemon. There is a way to knit multiple ompi-servers into a >> broader network (e.g., to connect processes that cannot directly access a >> server due to network segmentation), but it's a tad tricky - let me know if >> you require it and I'll try to help. >> If you have trouble wiring them all into a single communicator, you might >> ask separately about that and see if one of our MPI experts can provide >> advice (I'm just the RTE grunt). >> HTH - let me know how this works for you and I'll incorporate it into future >> OMPI releases. >> Ralph >> >> >> On Apr 24, 2010, at 1:49 AM, Krzysztof Zarzycki wrote: >> >> Hi Ralph, >> I'm Krzysztof and I'm working with Grzegorz Maj on this our small >> project/experiment. >> We definitely would like to give your patch a try. But could you please >> explain your solution a little more? >> You still would like to start one mpirun per mpi grid, and then have >> processes started by us to join the MPI comm? >> It is a good solution of course. >> But it would be especially preferable to have one daemon running >> persistently on our "entry" machine that can handle several mpi grid starts. >> Can your patch help us this way too? >> Thanks for your help! >> Krzysztof >> >> On 24 April 2010 03:51, Ralph Castain <r...@open-mpi.org> wrote: >>> >>> In thinking about this, my proposed solution won't entirely fix the >>> problem - you'll still wind up with all those daemons. I believe I can >>> resolve that one as well, but it would require a patch. >>> >>> Would you like me to send you something you could try? Might take a couple >>> of iterations to get it right... >>> >>> On Apr 23, 2010, at 12:12 PM, Ralph Castain wrote: >>> >>>> Hmmm....I -think- this will work, but I cannot guarantee it: >>>> >>>> 1. launch one process (can just be a spinner) using mpirun that includes >>>> the following option: >>>> >>>> mpirun -report-uri file >>>> >>>> where file is some filename that mpirun can create and insert its >>>> contact info into it. This can be a relative or absolute path. This process >>>> must remain alive throughout your application - doesn't matter what it >>>> does. >>>> It's purpose is solely to keep mpirun alive. >>>> >>>> 2. set OMPI_MCA_dpm_orte_server=FILE:file in your environment, where >>>> "file" is the filename given above. This will tell your processes how to >>>> find mpirun, which is acting as a meeting place to handle the >>>> connect/accept >>>> operations >>>> >>>> Now run your processes, and have them connect/accept to each other. >>>> >>>> The reason I cannot guarantee this will work is that these processes >>>> will all have the same rank && name since they all start as singletons. >>>> Hence, connect/accept is likely to fail. >>>> >>>> But it -might- work, so you might want to give it a try. >>>> >>>> On Apr 23, 2010, at 8:10 AM, Grzegorz Maj wrote: >>>> >>>>> To be more precise: by 'server process' I mean some process that I >>>>> could run once on my system and it could help in creating those >>>>> groups. >>>>> My typical scenario is: >>>>> 1. run N separate processes, each without mpirun >>>>> 2. connect them into MPI group >>>>> 3. do some job >>>>> 4. exit all N processes >>>>> 5. goto 1 >>>>> >>>>> 2010/4/23 Grzegorz Maj <ma...@wp.pl>: >>>>>> Thank you Ralph for your explanation. >>>>>> And, apart from that descriptors' issue, is there any other way to >>>>>> solve my problem, i.e. to run separately a number of processes, >>>>>> without mpirun and then to collect them into an MPI intracomm group? >>>>>> If I for example would need to run some 'server process' (even using >>>>>> mpirun) for this task, that's OK. Any ideas? >>>>>> >>>>>> Thanks, >>>>>> Grzegorz Maj >>>>>> >>>>>> >>>>>> 2010/4/18 Ralph Castain <r...@open-mpi.org>: >>>>>>> Okay, but here is the problem. If you don't use mpirun, and are not >>>>>>> operating in an environment we support for "direct" launch (i.e., >>>>>>> starting >>>>>>> processes outside of mpirun), then every one of those processes thinks >>>>>>> it is >>>>>>> a singleton - yes? >>>>>>> >>>>>>> What you may not realize is that each singleton immediately >>>>>>> fork/exec's an orted daemon that is configured to behave just like >>>>>>> mpirun. >>>>>>> This is required in order to support MPI-2 operations such as >>>>>>> MPI_Comm_spawn, MPI_Comm_connect/accept, etc. >>>>>>> >>>>>>> So if you launch 64 processes that think they are singletons, then >>>>>>> you have 64 copies of orted running as well. This eats up a lot of file >>>>>>> descriptors, which is probably why you are hitting this 65 process >>>>>>> limit - >>>>>>> your system is probably running out of file descriptors. You might >>>>>>> check you >>>>>>> system limits and see if you can get them revised upward. >>>>>>> >>>>>>> >>>>>>> On Apr 17, 2010, at 4:24 PM, Grzegorz Maj wrote: >>>>>>> >>>>>>>> Yes, I know. The problem is that I need to use some special way for >>>>>>>> running my processes provided by the environment in which I'm >>>>>>>> working >>>>>>>> and unfortunately I can't use mpirun. >>>>>>>> >>>>>>>> 2010/4/18 Ralph Castain <r...@open-mpi.org>: >>>>>>>>> Guess I don't understand why you can't use mpirun - all it does is >>>>>>>>> start things, provide a means to forward io, etc. It mainly sits there >>>>>>>>> quietly without using any cpu unless required to support the job. >>>>>>>>> >>>>>>>>> Sounds like it would solve your problem. Otherwise, I know of no >>>>>>>>> way to get all these processes into comm_world. >>>>>>>>> >>>>>>>>> >>>>>>>>> On Apr 17, 2010, at 2:27 PM, Grzegorz Maj wrote: >>>>>>>>> >>>>>>>>>> Hi, >>>>>>>>>> I'd like to dynamically create a group of processes communicating >>>>>>>>>> via >>>>>>>>>> MPI. Those processes need to be run without mpirun and create >>>>>>>>>> intracommunicator after the startup. Any ideas how to do this >>>>>>>>>> efficiently? >>>>>>>>>> I came up with a solution in which the processes are connecting >>>>>>>>>> one by >>>>>>>>>> one using MPI_Comm_connect, but unfortunately all the processes >>>>>>>>>> that >>>>>>>>>> are already in the group need to call MPI_Comm_accept. This means >>>>>>>>>> that >>>>>>>>>> when the n-th process wants to connect I need to collect all the >>>>>>>>>> n-1 >>>>>>>>>> processes on the MPI_Comm_accept call. After I run about 40 >>>>>>>>>> processes >>>>>>>>>> every subsequent call takes more and more time, which I'd like to >>>>>>>>>> avoid. >>>>>>>>>> Another problem in this solution is that when I try to connect >>>>>>>>>> 66-th >>>>>>>>>> process the root of the existing group segfaults on >>>>>>>>>> MPI_Comm_accept. >>>>>>>>>> Maybe it's my bug, but it's weird as everything works fine for at >>>>>>>>>> most >>>>>>>>>> 65 processes. Is there any limitation I don't know about? >>>>>>>>>> My last question is about MPI_COMM_WORLD. When I run my processes >>>>>>>>>> without mpirun their MPI_COMM_WORLD is the same as MPI_COMM_SELF. >>>>>>>>>> Is >>>>>>>>>> there any way to change MPI_COMM_WORLD and set it to the >>>>>>>>>> intracommunicator that I've created? >>>>>>>>>> >>>>>>>>>> Thanks, >>>>>>>>>> Grzegorz Maj >>>>>>>>>> _______________________________________________ >>>>>>>>>> users mailing list >>>>>>>>>> us...@open-mpi.org >>>>>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>>>>>>>> >>>>>>>>> >>>>>>>>> _______________________________________________ >>>>>>>>> users mailing list >>>>>>>>> us...@open-mpi.org >>>>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>>>>>>>> >>>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> users mailing list >>>>>>>> us...@open-mpi.org >>>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> users mailing list >>>>>>> us...@open-mpi.org >>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>>>>>> >>>>>>> >>>>>> >>>>> >>>>> _______________________________________________ >>>>> users mailing list >>>>> us...@open-mpi.org >>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>>> >>> >>> >>> _______________________________________________ >>> users mailing list >>> us...@open-mpi.org >>> http://www.open-mpi.org/mailman/listinfo.cgi/users >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users >> > <client.c><server.c>_______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users
