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Subject: Re: [OMPI devel] How is a MPI process launched ?
From: Leo P. (leo_7892003_at_[hidden])
Date: 2010-04-26 23:05:51


Hi Ralph, Is there some reason why you don't just use MPI_Comm_spawn? This is precisely what it was created to do. You can still execute it from a singleton, if you don't want to start your first process via mpirun (and is there some reason why you don't use mpirun???). The reason why i am using MPI_Comm_spawn and singleton is i am going to route the MPI Communication (btl and OOB) from another computer before it reaches it intended destination. :) Yes, you -could- hack the MPI code to do this. Starting from scratch, with little knowledge of the code base - figure on taking awhile. I could probably come up with a way to do it, but this would have to be a very low priority for me. I am trying to learn the OpenMPI code base and i know its going to take time. Now i need to understand how the processes are started and made part of MPI_Comm_World. I really want to do this but i need help. If you can suggest how this can be done, i would really appreciate a lot. Leo ________________________________ From: Ralph Castain <rhc_at_[hidden]> To: Open MPI Developers <devel_at_[hidden]> Sent: Tue, 27 April, 2010 6:44:49 AM Subject: Re: [OMPI devel] How is a MPI process launched ? Ummmm....I sincerely hope you are kidding :-) Is there some reason why you don't just use MPI_Comm_spawn? This is precisely what it was created to do. You can still execute it from a singleton, if you don't want to start your first process via mpirun (and is there some reason why you don't use mpirun???). Yes, you -could- hack the MPI code to do this. Starting from scratch, with little knowledge of the code base - figure on taking awhile. I could probably come up with a way to do it, but this would have to be a very low priority for me. On Apr 26, 2010, at 12:12 PM, Leo P. wrote: Hi Ralph, > > >Thank you for your response. Really appreciate it as usual. :) > >It depends - if you have an environment like slurm, sge, or torque, then we use that to launch our daemons on each node. Otherwise, we default to using ssh. > > >Once the daemons are launched, we then tell the daemons what processes each is to run. So it is a two-stage launch procedure. > > >Ralph after starting the orte_deamon > 1. what is the role of ssh then ? > 2. Also i am assuming HNP is created before using ssh. Am i right ? > 3. Also Ralph i would to know how i can tell the daemon to run a process ? >Ralph i am tying to create run a simple experiment where i can create a simple process between two computer using SSH module without using mpirun. I would to hack the mpi library so that i can send a simple "Hello World " from process A running in computer A to process B running in computer B. I would be create both the process myself. HOPE I AM BEING CLEAR. > > >Basically what i am saying is i would to create the MPI_COMM_WORLD comprising of two process Process A and Process B. For that i would to create a functions called Create_Process_A and Create_Process_B and Send_Message by utilizing Open MPI source code. > > >Also, I know i should be looking into PLM subsystem, RMAPS subsystem, ODLS subsystem, and ORTED subsystem. But Ralph if you guide me a bit i can finish the experiment with less sleepless night, headache, and stress. > > >Leo P > > > > >On Apr 26, 2010, at 2:22 AM, Leo P. wrote: > >Hi everyone, >> >> >>I wanted to know how OpenMPI launches a MPI process in a cluster environment. I am assuming if the process lifecycle management it will be using rsh. >> >> >> >> >>Anyhelp would be greatly appreciated. >> >> >>_______________________________________________ >>devel mailing list >>devel_at_[hidden] >>http://www.open-mpi.org/mailman/listinfo.cgi/devel > >_______________________________________________ >devel mailing list >devel_at_[hidden] >http://www.open-mpi.org/mailman/listinfo.cgi/devel