Hi Rupsa, The error message could be better. By "Invalid port", it actually meant the connection was timed out. So your 2-second time out actually worked. You should use MPI_Comm_set_errhandler​ to set error handler to MPI_ERRORS_RETURN​, so that your application can check error and respond accordingly. The default error handler is to abort. As I checked, the current code actually will leak resources when timeout happens. I just created this issue -- https://github.com/pmodels/mpich/issues/5815 -- to track it. -- Hui Zhou [https://opengraph.githubassets.com/f9215523be8f812ac3716771553a3d691ec7f493ddeb590e541727c7eb0340eb/pmodels/mpich/issues/5815]<https://github.com/pmodels/mpich/issues/5815> ch4/ofi: better error handling in MPI_Comm_{accept,connect} · Issue #5815 · pmodels/mpich<https://github.com/pmodels/mpich/issues/5815> In MPIDI_OFI_dynamic_send and MPIDI_OFI_dynamic_recv, when error happens, we should try cancel the send or recv. Otherwise, we may leave or accumulated unclosed handle in libfabric. Separately, whe... github.com ________________________________ From: Rupsa Chakraborty <[email protected]> Sent: Saturday, January 29, 2022 1:29 AM To: Zhou, Hui <[email protected]>; [email protected] <[email protected]> Cc: [email protected] <[email protected]> Subject: Re: [mpich-discuss] How to gracefully exit an MPI server process when it is waiting on MPI_Comm_accept Hi Hui, Joachim, Thanks for the information. I am not able to find in the internet a clear example as to how to populate MPI_Info and use it with MPI_Comm_accept. I tried to do the following, but this is giving errors as shown below. Could you provide a small example to set up a timeout with MPI_Comm_accept? Do I need to populate port info too with MPI_Info? MPI_Init(NULL, NULL); char portName[MPI_MAX_PORT_NAME]; MPI_Open_port(MPI_INFO_NULL, portName); MPI_Info info; MPI_Info_create( &info ); MPI_Info_set(info, "timeout", "2"); MPI_Comm intercomm; MPI_Comm_accept(portName, info, 0, MPI_COMM_SELF, &intercomm); Error: $ ./server Waiting to accept.... Abort(671693606) on node 0 (rank 0 in comm 0): Fatal error in internal_Comm_accept: Invalid port, error stack: internal_Comm_accept(102)....: MPI_Comm_accept(port_name=tag#0$connentry#020098ADAC1785B70000000000000000$, info=0x9c000002, 0, MPI_COMM_SELF, newcomm=0x7f79b17dbcb8) failed MPID_Comm_accept(442)........: dynamic_intercomm_create(400): peer_intercomm_create(334)...: (unknown)(): Invalid port Regards, Rupsa On Fri, Jan 28, 2022 at 8:47 PM Joachim Protze <[email protected]<mailto:[email protected]>> wrote: Hi, since you have a separate thread for the accept, you could just set a flag at the main thread, open a connection from the main thread to match the accept. The accept thread sees the flag, immediately closes the connection and leaves the while loop. - Joachim Am 28.01.22 um 05:54 schrieb Rupsa Chakraborty via discuss:

Hello,

I am asking this question in this forum as I had already asked this question in stack overflow and did not receive any answer/comment: https://stackoverflow.com/questions/70745740/how-to-gracefully-exit-an-mpi-s... <https://stackoverflow.com/questions/70745740/how-to-gracefully-exit-an-mpi-server-process-when-it-is-waiting-on-mpi-comm-acce>

My concern is as follows: I have an MPI server program that calls MPI_Comm_accept, in an infinite loop, on a separate thread. The main thread spawns this thread and in parallel does some other work. At some point of time the main thread decides to exit. It closes the port using MPI_Close_port(portName), however the MPI_Comm_accept() is still waiting for connection requests.

My question is: - How does the main thread exit gracefully? Is there an equivalent of socket close in MPI? I am using mpich which I can use from main thread?

- Is there anyway I can set timeout to the MPI_Comm_accept call?

Here is a dummy code that looks similar to my server code:

|// MPI Server Program void accept(std::string portName) { while (true) { MPI_Comm intercomm; MPI_Comm_accept(portName.c_str(), MPI_INFO_NULL, 0, MPI_COMM_SELF, &intercomm); // handle connection MPI_Comm_disconnect(&intercomm); } } int main() { char ch; MPI_Init(NULL, NULL); char portName[MPI_MAX_PORT_NAME]; MPI_Open_port(MPI_INFO_NULL, portName); publishName("nameServerFile.txt", "ocean", std::string(portName)); std::thread th(&accept, std::string(portName)); // do something MPI_Close_port(portName); std::cout <<"\nClosed port" << std::endl; th.join(); // main thread waits infinitely at this join // as child thread is still waiting on MPI_Comm_accept MPI_Finalize(); }|

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