FFTW Home Page. Configure problem with fftw. Well, I *really* never use CFLAGS, but CPPFLAGS instead (which basically hase the same effect; I just did not remember that very moment, and unfortunately only tested configure, not make). But anyway, we addressed that problem already in an earlier thread and there I proposed to write a patch, if I find the time. Needless to say, I didn't find it. However, this morning I took it and changed configure.ac to be more portable and use standard autotools macros. As pkg-config is known to be the tool of choice for additional packages, the patch uses it to check for FFTW and PLPlot.
It uses PLPlot by default and complains if it is not present, but you can switch it of by specifying the option --without-plplot to configure. All you now have to check, if your software is installed in non-standard locations, is that the PKG_CONFIG_PATH environment variable includes you special paths. Fortunately configure tells you that information, if anything fails. Best regards Jan. [gmx-users] Installation problem:fftw3f lib. not found. Fast Fourier Transform. (Discrete Fourier Transform) (Fast Fourier Transform) Written by Paul Bourke June 1993 This document describes the Discrete Fourier Transform (DFT), that is, a Fourier Transform as applied to a discrete complex valued series. For a continuous function of one variable f(t), the Fourier Transform F(f) will be defined as: and the inverse transform as where j is the square root of -1 and e denotes the natural exponent Consider a complex series x(k) with N samples of the form where x is a complex number Further, assume that that the series outside the range 0, N-1 is extended N-periodic, that is, x k = x k+N for all k.
The inverse transform will be defined as Of course although the functions here are described as complex series, real valued series can be represented by setting the imaginary part to 0. The following diagrams show the relationship between the series index and the frequency domain sample index. The highest positive (or negative) frequency sample is called the Nyquist frequency. Shifting.