Thanks, Bland and Lu. You are right. These functions (such as MPI_Comm_accept, MPI_Comm_connect, MPI_Intercomm_merge) can help me to get a new intra-communicator which contains ALL MPI processes. Now, I have a more complicated example: I have a server and a client. After they merge into an intra-communicator by using connect/accept/merge fucntions, another client would plant to join them, too. I thought that the code is simular, but the code CAN'T work: Second client CAN'T connect. The new comm CAN'T accept. They all BLOCK. As you see, the second client BLOCKs at MPI_Comm_connect, and processes of newcomm BLOCK at MPI_Comm_accept. What's Wrong with my code? //server #include "mpi.h" int main(int argc, char *argv[]) { MPI_Comm client, client2, newcomm, newcomm2; MPI_Status status; char port_name[MPI_MAX_PORT_NAME]; char port_name2[MPI_MAX_PORT_NAME]; int size, again, rank, myrank; MPI_Init(&argc, &argv); MPI_Open_port(MPI_INFO_NULL, port_name);//OK MPI_Comm_accept(port_name, MPI_INFO_NULL, 0, MPI_COMM_WORLD,&client);//OK MPI_Intercomm_merge(client,11,&newcomm);//OK MPI_Barrier(newcomm);//OK MPI_Open_port(MPI_INFO_NULL, port_name2);// OK MPI_Comm_accept(port_name2, MPI_INFO_NULL, 0, newcomm,&client2);// BLOCK here, Wath's wrong? MPI_Intercomm_merge(client2,12,&newcomm2); MPI_Barrier(newcomm2); MPI_Close_port(port_name); MPI_Comm_disconnect(&client); MPI_Close_port(port_name2); MPI_Comm_disconnect(&client2); MPI_Finalize(); return 0; } //first client #include "mpi.h" int main( int argc, char **argv ) { MPI_Comm server,newcomm,newcomm2,client2; char port_name[MPI_MAX_PORT_NAME]; char port_name2[MPI_MAX_PORT_NAME]; int size,rank; MPI_Init( &argc, &argv ); strcpy( port_name, argv[1] ); MPI_Comm_connect( port_name, MPI_INFO_NULL, 0, MPI_COMM_SELF,&server );//OK MPI_Intercomm_merge(server,11,&newcomm);//OK MPI_Barrier(newcomm);//OK MPI_Open_port(MPI_INFO_NULL, port_name2);//OK MPI_Comm_accept(port_name2, MPI_INFO_NULL, 0, newcomm,&client2);// BLOCK here, Wath's wrong? MPI_Intercomm_merge(client2,12,&newcomm2); MPI_Barrier(newcomm2); MPI_Close_port(port_name2); MPI_Comm_disconnect(&client2); MPI_Comm_disconnect( &server ); MPI_Finalize(); return 0; } //second client #include "mpi.h" int main( int argc, char **argv ) { MPI_Comm server,newcomm; char port_name[MPI_MAX_PORT_NAME]; int size,rank; MPI_Init( &argc, &argv ); strcpy( port_name, argv[1] );//OK MPI_Comm_connect( port_name, MPI_INFO_NULL, 0, MPI_COMM_SELF,&server );// BLOCK here, Wath's wrong? MPI_Comm_size(MPI_COMM_WORLD, &size); MPI_Intercomm_merge(server,11,&newcomm); MPI_Barrier(newcomm); MPI_Comm_disconnect( &server ); MPI_Finalize(); return 0; } At 2015-01-23 23:14:06, "Wesley Bland" <[email protected]> wrote: The size of MPI_COMM_WORLD will never change. That communicator is set at initialization time and is not ever modified. However, when you finish connect/accept, you get a new communicator which you can merge into an intra-communicator which functions exactly like MPI_COMM_WORLD. Don’t be attached to the variable name MPI_COMM_WORLD. It’s just a variable and you can use a different one with very little extra work. Thanks, Wesley On Thu, Jan 22, 2015 at 6:14 PM, haozi <[email protected]> wrote: Thanks, Lu. My simple code is as following. //server #include "mpi.h" int main(int argc, char *argv[]) { MPI_Comm client; MPI_Status status; char port_name[MPI_MAX_PORT_NAME]; int size, again; MPI_Init(&argc, &argv); MPI_Comm_size(MPI_COMM_WORLD, &size); MPI_Open_port(MPI_INFO_NULL, port_name); printf("server port_name is %s\n\n", port_name); MPI_Comm_accept(port_name, MPI_INFO_NULL, 0, MPI_COMM_WORLD,&client); MPI_Comm_size(MPI_COMM_WORLD, &size); printf("At server, comm_size=%d @ MPI_COMM_WORLD=%x, Client_World=%x\n",size,MPI_COMM_WORLD, client); MPI_Comm_size(client, &size); printf("At server, client_size=%d @ MPI_COMM_WORLD=%x, Client_World=%x\n",size,MPI_COMM_WORLD, client); MPI_Comm_disconnect(&client); MPI_Finalize(); return 0; } //client #include "mpi.h" int main( int argc, char **argv ) { MPI_Comm server; char port_name[MPI_MAX_PORT_NAME]; int size; MPI_Init( &argc, &argv ); strcpy( port_name, argv[1] ); printf("server port name:%s\n",port_name); MPI_Comm_connect( port_name, MPI_INFO_NULL, 0, MPI_COMM_WORLD,&server ); MPI_Comm_size(MPI_COMM_WORLD, &size); printf("At client, comm_size=%d @ MPI_COMM_WORLD=%x, Server_World=%x\n",size,MPI_COMM_WORLD,server); MPI_Comm_size(server, &size); printf("At client, server_size=%d @ MPI_COMM_WORLD=%x, Server_World=%x\n",size,MPI_COMM_WORLD,server); MPI_Comm_disconnect( &server ); MPI_Finalize(); return 0; } The run command is as following. mpiexec -n 1 ./server mpiexec -n 1 ./client BUT, the SIZE is 1, NOT 2. My question is as before: How does the size of MPI_COMM_WORLD change to 2 ? At 2015-01-23 00:30:43, "Huiwei Lu" <[email protected]> wrote: You may take a look at MPI_Comm_accept and MPI_Comm_connect, which will connect a new client process to a server process. See Chap. 10 of MPI 3.0 standard (www.mpi-forum.org/docs/mpi-3.0/mpi30-report.pdf) for a detail example. -- Huiwei Lu Postdoc Appointee Mathematics and Computer Science Division Argonne National Laboratory http://www.mcs.anl.gov/~huiweilu/ On Thu, Jan 22, 2015 at 9:41 AM, haozi <[email protected]> wrote: Hi, guys. This web page (http://wiki.mpich.org/mpich/index.php/PMI_v2_Design_Thoughts) says: Singleton init. This is the process by which a program that was not started with mpiexec can become an MPI process and make use of all MPI features, including MPI_Comm_spawn, needs to be designed and documented, with particular attention to the disposition of standard I/O. Not all process managers will want to or even be able to create a new mpiexec process, so this needs to be negotiated. Similarly, the dispostion of stdio needs to be negotiated between the singleton process and the process manager. To address these issues, a new singleton init protocol has been implemented and tested with the gforker process manager. I am very interested in this function. Can this function solve the following question: At beginning, the MPI job uses the mpiexec commond to start three MPI processes. That is to say, there are three MPI processes in MPI_COMM_WORLD. At some time, the job find itself to need another MPI process to cooperate the three MPI processes. So the question is: Could PMI help an non-MPI process to become a MPI process of the current MPI_COMM_WORLD? That is to say, Could the non-MPI process use the PMI function to become a member process of the current MPI job which would have FOUR MPI processes in MPI_COMM_WORLD? Is there some method to solve question? Is anybody have some example? Thandks!!! _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss