fftw2 2.1.5-3 (armhf binary) in ubuntu xenial

 This library computes Fast Fourier Transforms (FFT) in one or more dimensions.
 It is extremely fast. This package contains the shared library version of the
 fftw libraries in double precision.
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 To get the static library and the header files you need to install fftw-dev.
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 For documentation and test programs, install fftw-docs