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1answer
119 views

Time array from frequency array in FFT using Python

I have done a Fourier transformation of two signals (in time) $S_1(t),S_2(t)$ using numpy's fft which will give me $S_1(f),S_2(f)$. The corresponding frequency grid ...
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1answer
43 views

Which version of FFTW

At the moment, I'm installing the "GADGET-2" application. In its documentation it says "Note that the MPI-capable version 2.x of FFTW is required, the new version 3 lacks MPI capability at this point. ...
1
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1answer
118 views

DST using FFT routine

Please can you help me with my problem? On Wikipedia, in article Discrete sine transform, this is written (chapter Computation): "Although the direct application of these formulas would require O(N2) ...
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2answers
66 views

A function as a sum of serie of modified FFT coeff. of another function - multiplied by sum number

I solve such a problem. Lets have a function $Y=\sum_{k=-\infty}^\infty i\hat Y e^{ik\pi y}$ and then I have a function which is defined as $X=\sum_{k=-\infty}^\infty ik^2\hat Y e^{ik\pi y}$. I ...
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1answer
476 views

MPI-based Implementations of FFT

In a numerical computation, I am required to take a multi-dimensional FFT on a distributed-memory cluster. The data is currently distributed using a distributed array in PETSc (DMDA). I initial ...
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0answers
98 views

FFT - function only in sine series? Can be done with MKL / Lapack?

please can I ask, how one can make from function sine series (Fourier transform) with MKL? I can do "normal" exponential FFT with MKL (Lapack of course), how can I say that I want only sine series? ...
1
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1answer
121 views

Discrete convolution

please can I ask a bit stupid question? Let say I need to solve an equation in a form $\frac{\partial X}{\partial t}=\sum_k M_k * X_{n-k}$ How can I do the discrete convolution numerically? I will say ...
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1answer
546 views

Fast (approximate) evaluation of Chebyshev polynomial

Is there a preferred way how to implement a fast (approximate) evaluation of the Chebyshev interpolation polynomial on uniform grid (given the function values at the Chebyshev nodes)? My problem is ...
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4answers
479 views

Scalability of Fast Fourier Transform (FFT)

To use the Fast Fourier Transform (FFT) on uniformly sampled data, e.g. in connection with PDE solvers, it is well known that the FFT is an $\mathcal{O}(n\log(n)$) algorithm. How well do the FFT scale ...
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1answer
261 views

How can I tell VASP 5.2 is compiled with FFTW3?

When VASP 5 was released, the performance was mostly slower than our make of VASP 4.6. I wrote it off as an optimization issue, and went on in my life. Then, in VASP 5.2, with the release notes, I ...