我运行了一个包含3个以上进程的简单MPI Python程序。 例如：
mpiexec -host master,w1,w2,w3 python code.py
导致错误：
ssh: Could not resolve hostname w3: Name or service not known
ORTE was unable to reliably start one or more daemons.
This usually is caused by:
* not finding the required libraries and/or binaries on
one or more nodes. Please check your PATH and LD_LIBRARY_PATH
settings, or configure OMPI with --enable-orterun-prefix-by-default
* lack of authority to execute on one or more specified nodes.
Please verify your allocation and authorities.
* the inability to write startup files into /tmp (-tmpdir/orte_tmpdir_base).
Please check with your sys admin to determine the correct location to use.
* compilation of the orted with dynamic libraries when static are required
(e.g., on Cray). Please check your configure cmd line and consider using
one of the contrib/platform definitions for your system type.
* an inability to create a connection back to mpirun due to a
lack of common network interfaces and/or no route found between
them. Please check network connectivity (including firewalls
and network routing requirements).
但是，如果我用w1，w2，w3中的任意两个运行程序，它就可以了。 EX：
mpiexec -host master,w1,w3 python code.py
而且，这是代码
import random
import numpy as np
from mpi4py import MPI
comm = MPI.COMM_WORLD
rank = comm.rank
size = comm.size
if rank ==0:
print rank, 'worker'
else:
print rank, 'worker'
我该如何解决？