I am new to Fortran. Is there an ultimate best library for FFT for Fortran (95)? I found this one FFTPACK. I am not sure if this is the best one. Is there anywhere a simple example how to use it? I have huge time files (260 MB each) that I like to read in Fortran and perform FFT and store the results in HDF5 format. I almost do the same thing with C++ using FFTW, but I it is a bit slow. There is a wrapper for FFTW for Fortran, but I wondered if a pure Fortran routine will be faster? thanks.