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 > > > >
