The important thing here is, that you tell
which Linux, you are using ..
Like Ubuntu 9.10 Karmic, Fedora 12, CentOS 5.x, etc.
And also please explain, why you are not installing
fftw3 with your "Package Manager". Or with # yum / apt-get .. ?
→ → fftw3-devel / libfftw3-dev / fftw-devel / libfftw3-devel
.. The fftw3 development package has different names
in different Linux's.)
Just guessing, you are trying to compile fftw3 for OpenMX ?