/usr/share/doc/libfftw3-mpi-dev/README is in libfftw3-mpi-dev 3.3.3-2ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libfftw3-mpi-dev/../libfftw3-mpi3/README
/usr/share/doc/libfftw3-mpi-dev/../libfftw3-mpi3/README