remote-exec required by some MPIs (DDT)

When using the MPMD variants of MPICH 3, MPICH 4, or Intel MPI, you can use mpirun to start all the processes, then attach to them while they are inside MPI_Init.

This method is often faster than the generic method, but requires the remote-exec facility to be correctly configured if processes are being launched on a remote machine. For more information on remote-exec, see Connecting to compute nodes and remote programs (remote-exec) and Choose hosts on Attach to running programs.

Note

If Linaro DDT is running in the background (for example, ddt &) this process may get stuck. Some SSH versions cause this behavior when asking for a password. If this happens to you, go to the terminal and use the fg or similar command to make Linaro DDT a foreground process, or run Linaro DDT again, without using &.

If Linaro DDT cannot find a password-free way to access the cluster nodes then you will not be able to use the specialized startup options. Instead, you can use generic, although startup may be slower for large numbers of processes.

In addition to the listed MPI implementations above, all MPI implementations except for Cray MPT Linaro DDT require password-free access to the compute nodes when explicitly starting by attaching.