You can't use "FFTW" library on SX-ACE.
But you can use FFT by "MathKeisan" library that optimized for SX.
MathKeisan　MathKeisan User's Guide（Authorization required）

If you install any library and application to your disk, our permits are not necessary.
 
If you expect that center install any library and application to a whole of system, please contact us from the following web form:
Inquiry / Request form
 

Please note that we may not permit or we may ask to install with yourself, depending on the kind of library and application.

You can't use the shared library(.so:Dynamic Shared Object) on SX. SX supports only static library.
Please use just a object code file or use archiving file(.a: Please change your shared library with "sxar" command).

sxar vr (library name).a (library name).so

You can use these libraries on our all system.
We are providing the library, MathKeisan, for SX-ACE user. This library include Blas and Lapack and other library. Please see the following page about the detail of use.
How to use MathKeisan
 
And we are providing the library, IntelMKL, for OCTOPUS user. This library include Lapack and Blas also. Please see the following page about the detail of use.

How to use IntelMKL(OCTOPUS)