$ wget https://download.open-mpi.org/release/open-mpi/v2.1/openmpi-2.1.6.tar.gz
$ tar xvf openmpi-2.1.6.tar.gz
$ cd openmpi-2.1.6
$ mkdir build
$ cd build
$ ../configure --prefix=/opt/openmpi-2.1.6 CC=gcc CXX=g++ --enable-mpi-cxx
$ make -j
$ make install