I thought mpirun always assumes default behavior when -np <number of processes> is not given. With hydra, it default to 1. Openmpi would default to number of hardware threads I believe. Zhifeng, could you duplicate the error with a simpler FORTRAN program and post your source code so I can try reproduce? — Hui Zhou T: 630-252-3430 On Nov 13, 2018, at 10:27 AM, Si, Min via discuss <[email protected]<mailto:[email protected]>> wrote: Hi Zhifeng, You have to always execute the MPI program by using mpirun or mpiexec with -np <number of processes>. At MPI_Init, the process tries to read information (e.g., MPI rank, number of processes) from the PMI server which is another process launched by the mpiexec command. This information is necessary for MPI library to initialize communication (e.g., connecting two processes). Best regards, Min On 2018/11/04 10:27, Zhifeng Yang via discuss wrote: Hi After I installed mpich and used it in a FORTRAN code. There is an error while running this FORTRAN code called real.exe by using the following command $./real.exe or $mpirun ./real.exe real.exe: error: _get_addr: No such file or directory real.exe: error: _get_addr: No such file or directory real.exe: error: _get_addr: No such file or directory Fatal error in MPI_Init: Other MPI error, error stack: MPIR_Init_thread(784).....: MPID_Init(1323)...........: channel initialization failed MPIDI_CH3_Init(120).......: MPID_nem_init_ckpt(852)...: MPIDI_CH3I_Seg_commit(364): PMI_Barrier returned -1 But while using mpirun with specifying number of processors. as follows $mpirun -np 1 ./real.exe There is no error any more. I am not sure why? do you have any explanation? Thank you very much Best regards Zhifeng _______________________________________________ discuss mailing list [email protected]<mailto:[email protected]> To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss _______________________________________________ discuss mailing list [email protected]<mailto:[email protected]> To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss