I've looked through the hydra docs but I haven't found a flag or anything else that would let me disable it spawning in tree mode, if MPICH even does that.

I was able to kind of rectify the error using OpenMPI and specifying the "-mca plm_rsh_no_tree_spawn" flag


On 29 May 2014 14:54, Lu, Huiwei <huiweilu@mcs.anl.gov> wrote:
Hi Scott,

Check https://wiki.mpich.org/mpich/index.php/Using_the_Hydra_Process_Manager to see if it is what you want.

Best,
—
Huiwei

On May 29, 2014, at 6:37 AM, Scott O'Malley <scottyomalley@gmail.com> wrote:

> I have recently built a cluster of Raspberry Pi computers. When this was made up of a master node and 2 slave nodes there was no issue calling mpiexec across the cluster. When I add an additional node to the cluster bringing the size to 1 master and 3 slave nodes I get an error of "Host File Verification Failed". I've tested password-less SSH on all nodes and it's working correctly.
>
> I've done some googling of the error and set up and the only mention I've gotten to it was on this link here relating to OpenMPI - http://www.open-mpi.org/community/lists/users/2013/11/22940.php
>
> Is there a similar setup for MPICH and if so can someone link me to the correct documentation page?
>
> Cheers
>
> Scott
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--
- Scott