Hi Gilles, MPI provides explicit comparison functions to compare opaque handles, for communicators it is MPI_Comm_compare.
- Joachim ________________________________ From: users <users-boun...@lists.open-mpi.org> on behalf of Guillaume De Nayer via users <users@lists.open-mpi.org> Sent: Friday, June 24, 2022 5:13:17 PM To: users@lists.open-mpi.org <users@lists.open-mpi.org> Cc: Guillaume De Nayer <dena...@hsu-hh.de> Subject: Re: [OMPI users] Intercommunicator issue (any standard about communicator?) Thank you for these infos! On 06/24/2022 05:06 PM, Jeff Squyres (jsquyres) via users wrote: > Open MPI and MPICH are completely unrelated -- we're entirely different code > bases (note that Intel MPI is derived from MPICH). > > Case in point is what Gilles cited: Open MPI chose to implement MPI_Comm > handles as pointers, but MPICH chose to implement MPI_Comm handles as > integers. Hence, you can't really compare the MPI_Comm values from Open MPI > vs. MPI_Comm values from MPICH/Intel MPI -- they're fundamentally > representing different things. > > The MPI standard doesn't say anything about the values of MPI handles (e.g., > MPI_Comm handles). They're just a value that a user program can pass around. > When that handle is given to the MPI implementation (e.g., by passing it to > MPI_Send() or other MPI API), the only rule is that the MPI implementation > has to be able to map that handle into whatever back end data structures are > relevant to implement the concept of an MPI communicator. Hence: the handle > is meaningless to the application -- it's just an opaque value that the user > program can pass around. > > User applications *can* compare it to the value for MPI_COMM_NULL, but that's > about it. > > -- > Jeff Squyres > jsquy...@cisco.com > > ________________________________________ > From: users <users-boun...@lists.open-mpi.org> on behalf of Guillaume De > Nayer via users <users@lists.open-mpi.org> > Sent: Friday, June 24, 2022 8:29 AM > To: users@lists.open-mpi.org > Cc: Guillaume De Nayer > Subject: Re: [OMPI users] Intercommunicator issue (any standard about > communicator?) > > Hi Gilles, > > I'm using both openmpi and intel mpi. I have with both problem with the > communicators. Therefore, I tried to get some infos about them. > > Thx a lot for your help. > Have a nice day > > On 06/24/2022 02:14 PM, Gilles Gouaillardet via users wrote: >> Guillaume, >> >> MPI_Comm is an opaque handler that should not be interpreted by an end user. >> >> Open MPI chose to implement is as an opaque pointer, and MPICH chose to >> implement it as a 32 bits unsigned integer. >> The 44000000 value strongly suggests you are using MPICH and you are >> hence posting to the wrong mailing list >> >> >> Cheers, >> >> Gilles >> >> On Fri, Jun 24, 2022 at 9:06 PM Guillaume De Nayer via users >> <users@lists.open-mpi.org <mailto:users@lists.open-mpi.org>> wrote: >> >> Hi Gilles, >> >> MPI_COMM_WORLD is positive (44000000). >> >> In a short code I wrote I have something like that: >> >> MPI_Comm_dup(MPI_COMM_WORLD, &world); >> cout << "intra-communicator: " << "world" << "---" << hex << world >> << endl; >> >> It returns "84000006" (in hex). >> >> later I have: >> >> MPI_Comm_accept(port_name, MPI_INFO_NULL, 0, world, &interClient); >> cout << "intercommunicator interClient=" << interClient << endl; >> >> After connection from a third party client it returns "c4000003" (in >> hex). >> >> Both 84000006 and c4000003 are negative integer in dec. >> >> I don't know if it is "normal". Therefore I'm looking about rules on the >> communicators, intercommunicators. >> >> Regards, >> Guillaume >> >> >> On 06/24/2022 11:56 AM, Gilles Gouaillardet via users wrote: >> > Guillaume, >> > >> > what do you mean by (the intercommunicators are all negative"? >> > >> > >> > Cheers, >> > >> > Gilles >> > >> > On Fri, Jun 24, 2022 at 4:23 PM Guillaume De Nayer via users >> > <users@lists.open-mpi.org <mailto:users@lists.open-mpi.org> >> <mailto:users@lists.open-mpi.org <mailto:users@lists.open-mpi.org>>> >> wrote: >> > >> > Hi, >> > >> > I am new on this list. Let me introduce myself shortly: I am a >> > researcher in fluid mechanics. In this context I am using >> softwares >> > related on MPI. >> > >> > I am facing a problem: >> > - 3 programs forms a computational framework. Soft1 is a coupling >> > program, i.e., it opens an MPI port at the beginning. Soft2 >> and Soft3 >> > are clients, which connect to the coupling program using >> > MPI_Comm_connect. >> > - After the start and the connections of Soft2 and Soft3 with >> Soft1, it >> > hangs. >> > >> > I started to debug this issue and as usual I found another >> issue (or >> > perhaps it is not an issue): >> > - The intercommunicators I get between Soft1-Soft2 and >> Soft1-Soft3 are >> > all negative (running on CentOS 7 with infiniband Mellanox >> OFED driver). >> > - Is there some standard about communicator? I don't find anything >> > about >> > this topic. >> > - What is a valid communicator, intercommunicator? >> > >> > thx a lot >> > Regards >> > Guillaume >> > >> >> > > >
