[MPICH] DHCP assigned IP addresses and hostnames?

[Steve Kargl]

On Fri, Nov 17, 2006 at 03:31:03PM -0600, Ralph Butler wrote:
> I do not think these changes should be necessary.   But, I must confess
> that I no longer believe that I understand  what problem you are  
> trying to solve.  Also, using mpdboot
> should work just fine, but is merely an extra step if you are running  
> on a single host.
> 

Here's the problem.  My colleague has a laptop that gets
it IP address from a dhcp server and the server doesn't provide
a fully qualified domain name (FQDN).  The laptop's hostname
is set to fakename.foobar.org.  The real FQDN associated with
the IP address 128.X.Y.Z is D-128-X-Y-Z.dhcp4.washington.edu. 

If he starts mpd via
   mpdboot --ifhn=127.0.0.1 --ncpus=2 --file=.mpd.hosts
where .mpd.hosts contains "127.0.0.1:2"
then he gets

   mpdboot_fakename (handle_mpd_output 388): from mpd on 127.0.0.1,
   invalid port info:
   mpd failed: gethostbyname_ex failed for fakename

If he starts mpd via
   mpd --ifhn=127.0.0.1 --ncpus=2 --file=.mpd.hosts
then he gets
   mpd failed: gethostbyname_ex failed for fakename

It appears that although --ifhn=127.0.0.1 binds the daemon to
the localhost address, it does not set hostname (or some python
variable) to 'localhost' so gethostbyname_ex fails.

With dual-core CPUs in laptops today and quad-core CPUs coming
in the future, it is conceivable that one may want to run a
mpi application on the laptop.  In fact, the laptop could be
in a remote location without internet access, so binding mpd
to localhost seems like a logical thing to do when --ifhn=
is set to 127.0.0.1.

-- 
Steve