How to install parallel tool on Ubuntu 12.04 Precise 
As the package hasn't been debianised in Ubuntu yet we have to install it using the old school methods.
Follow link  and download the appropriate package. Once downloaded install it using dpkg.
wget http://download.opensuse.org/repositories/home:/tange/xUbuntu_12.04/all/parallel_20110422-1_all.deb dpkg -i parallel_20110422-1_all.deb type -a parallel 22:51:35 parallel is /usr/bin/parallel