Also, xmds expects that the fftw.h header file is in one of the /usr/include or the /usr/local/include directories, with the libraries in a sibling /usr/lib or /usr/local/lib directory. These are the standard locations. If the fftw installation is non-standard then your will need to set a FFTWDIR="..." environment macro (if one is not already set) pointing to the parent directory containing the /include and /lib sub-directories.

FFTW: if your fftw libraries and headers are installed in /usr/local/lib and /usr/local/include respectively (or some other directory such as /apps/fftw/lib and /apps/fftw/include) then you need to add --with-fftw-path=your-fftw-path to the configure script's arguments. For instance, if your fftw libraries are installed in /apps/fftw/lib and the headers are installed in /apps/fftw/include, then you should use --with-fftw-path=/apps/fftw as the option to the configure script.

MPI: if you wish to use mpi, then you must add --enable-mpi to the configure script's arguments