What is your system? PBS? You have to prescribe a pool of nodes with qsub and run mpiexec -n 1 (for example). Then when you launch additional mpi process dynamically, hydra will spawn new processes within the prescribed pool. If your original pool is a single host, then all new dynamic process will be on that single host. If you describe multiple hosts, I believe hydra will do round-robin style allocation, i.e. the next processes will go to host 2, host 3, …., host N, host 1 (circle back). This is my current understanding. Let me know whether you can confirm. — Hui Zhou On Nov 29, 2018, at 4:41 PM, Shuwei Zhao <[email protected]<mailto:[email protected]>> wrote: Hi Hui I cannot run mpiexec directly on my hosts because both rsh and ssh connections are disabled. I have to use qsub -P bnormal -pe dp 4 mpiexec ./my_exe to run my binary on remote hosts. Thanks Shuwei