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The modules do not have any effect during runtime.
Precision
On Unix, link to -lfftw3f (single) or -lfftw3l (long-double) instead of (or in addition to) -lfftw3 (double).
You can see all provided versions directly after you loaded an FFTW module with: ls ${LIBRARY_PATH%%:*}
Installation at HLRN
Fftw3 is build from source. The current version is build with several compilers. High end optimisation is used. read more
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