$ wget https://download.open-mpi.org/release/open-mpi/v4.0/openmpi-4.0.5.tar.bz2
$ tar xvf  openmpi-4.0.5.tar.bz2
$ cd openmpi-4.0.5
$ mkdir build
$ cd build
$ ../configure --prefix=/opt/openmpi-4.0.5 CC=gcc CXX=g++ --enable-mpi-cxx
$ make -j
$ make check
$ make install