File fft_fftw.cxx#

FFT routines using external libraries.

This file is part of BOUT++.

BOUT++ is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

BOUT++ is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with BOUT++. If not, see http://www.gnu.org/licenses/.

namespace bout

Provides access to the Hypre library, handling initialisation and finalisation.

Usage

#include <bout/hyprelib.hxx>

class MyClass { public:

private: HypreLib lib; };

This will then automatically initialise Hypre the first time an object is created, and finalise it when the last object is destroyed.

Contact: Ben Dudson, bd512@york.ac.uk

This file is part of BOUT++.

You should have received a copy of the GNU Lesser General Public License along with BOUT++. If not, see http://www.gnu.org/licenses/.

Explicit inversion of a 3x3 matrix a

If the matrix is singular (ill conditioned), the determinant is return. Otherwise, an empty std::optional is return

SNB model

namespace fft

Functions

void fft_init(bool fft_measure)#: Should the FFT functions find and use an optimised plan?

void fft_init(FFT_MEASUREMENT_FLAG fft_flag)#: Should the FFT functions find and use an optimised plan?

void fft_init(Options *options = nullptr)#

Should the FFT functions find and use an optimised plan?

If options is not nullptr, it should contain a bool called “fftw_measure”. If it is nullptr, use the global Options root

Array<dcomplex> rfft(const Array<BoutReal> &in)#: Returns the fft of a real signal in using fftw_forward.

Array<BoutReal> irfft(const Array<dcomplex> &in, int length)#

Take the inverse fft of signal in where the outputs are only reals. Requires the length of the original real signal

length is required because input signals to the forward transform of length n and n + 1 both produce ffts of length (n / 2) + 1 — i.e. it’s not possible to recover the length of the original signal from the fft alone.

Expects that in.size() == (length / 2) + 1

void rfft([[maybe_unused]] const BoutReal *in, [[maybe_unused]] int length, [[maybe_unused]] dcomplex *out)

void irfft([[maybe_unused]] const dcomplex *in, [[maybe_unused]] int length, [[maybe_unused]] BoutReal *out)

void DST([[maybe_unused]] const BoutReal *in, [[maybe_unused]] int length, [[maybe_unused]] dcomplex *out)

void DST_rev([[maybe_unused]] dcomplex *in, [[maybe_unused]] int length, [[maybe_unused]] BoutReal *out)

Variables

bool fft_initialised = {false}#: Have we set fft_measure?

FFT_MEASUREMENT_FLAG fft_measurement_flag = {FFT_MEASUREMENT_FLAG::estimate}#: Should FFTW find an optimised plan by measuring various plans?