gethostbyname fail after switching internet connections

Question

I often (but not always) get the following error when running MPI jobs after switching wifi hosts.

Fatal error in MPI_Init: Other MPI error, error stack:
MPIR_Init_thread(498)..............: 
MPID_Init(187).....................: channel initialization failed
MPIDI_CH3_Init(89).................: 
MPID_nem_init(320).................: 
MPID_nem_tcp_init(171).............: 
MPID_nem_tcp_get_business_card(418): 
MPID_nem_tcp_init(377).............: gethostbyname failed, MacBook-Pro.local     (errno 1)

Everything works fine in the coffee shop, and then when I come home, I get the above error. Nothing else has changed.

I've checked the /etc/hosts and /private/etc/hosts files, and they look okay -

##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.
##
127.0.0.1       localhost
255.255.255.255 broadcasthost

I can ping localhost, so the problem isn't exactly that localhost isn't resolved.

Rebooting always fixes the problem, but is there something simple I can do to "reset" my system so that it recognizes local host?

I don't have access to the details of the MPI initialization routines in the code I am running and am not making any explicit calls to gethostname.

I am using MPICH 3.1.4 (built Feb, 2015) and am running OSX 10.10.3

Answer 1

The answer is very simple - here is what seems to work.

I edited the file /etc/hosts (or /private/etc/hosts, in OSX) and added the line

127.0.0.1   macbook-pro.local

so now my hosts files looks like :

##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.
##
127.0.0.1   localhost
255.255.255.255 broadcasthost
127.0.0.1   macbook-pro.local