/usr/lib/libsrfftw_threads.so.2 is in sfftw2 2.1.5-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libsrfftw_threads.so.2.0.7
/usr/lib/libsrfftw_threads.so.2.0.7