Install and Configure MPICH2 on Ubuntu

The general procedure is described in
http://developer.amd.com/documentation/articles/pages/HPCHighPerformanceLinpack.aspx#four

I have encountered two cases where MPD on multiple nodes cannot communicate with each other:

1. The firewall prevents such communication, and
   
2. There are ambiguity in /etc/hosts.

For 1., we can disable iptables (the firewall commonly used in various Linux versions) and ufw (Ubuntu firewall) by the following commands:
sudo iptables -P INPUT ACCEPT
sudo iptables -P OUTPUT ACCEPT
sudo ufw disable

For 2., I just re-edit /etc/hosts to ensure all nodes are referred by their real IP addresses, instead of loop-back style addresses.