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Section Mesh::FFTs
Type integer
Default fftw_measure

The FFTs are performed in octopus with the help of FFTW and similar packages. Before doing the actual computations, this package prepares a "plan", which means that the precise numerical strategy to be followed to compute the FFT is machine/compiler-dependent, and therefore the software attempts to figure out which is this precise strategy (see the FFTW documentation for details). This plan preparation, which has to be done for each particular FFT shape, can be done exhaustively and carefully (slow), or merely estimated. Since this is a rather critical numerical step, by default it is done carefully, which implies a longer initial initialization, but faster subsequent computations. You can change this behaviour by changing this FFTPreparePlan variable, and in this way you can force FFTW to do a fast guess or estimation of which is the best way to perform the FFT.


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