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========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Copyright (C) 2011-2018 OpenFOAM Foundation
\\/ M anipulation |
-------------------------------------------------------------------------------
License
This file is part of OpenFOAM.
OpenFOAM is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
OpenFOAM 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 General Public License
for more details.
You should have received a copy of the GNU General Public License
along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
Description
Multi-dimensional renumbering used in the Numerical Recipes
fft routine. This version is recursive, so works in n-d :
determined by the length of array nn
\*---------------------------------------------------------------------------*/
#include "fftRenumber.H"
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
void Foam::fftRenumberRecurse
(
List<complex>& data,
List<complex>& renumData,
const labelList& nn,
label nnprod,
label ii,
label l1,
label l2
)
{
if (ii == nn.size())
{
// we've worked out the renumbering scheme. Now copy
// the components across
data[l1] = complex(renumData[l2].Re(),renumData[l2].Im());
}
else
{
// do another level of folding. First work out the
// multiplicative value of the index
nnprod /= nn[ii];
label i_1(0);
for (label i=0; i<nn[ii]; i++)
{
// now evaluate the indices (both from array 1 and to
// array 2). These get multiplied by nnprod to (cumulatively)
// find the real position in the list corresponding to
// this set of indices.
if (i<nn[ii]/2)
{
i_1 = i + nn[ii]/2;
}
else
{
i_1 = i - nn[ii]/2;
}
// go to the next level of recursion.
fftRenumberRecurse
(
data,
renumData,
nn,
nnprod,
ii+1,
l1+i*nnprod,
l2+i_1*nnprod
);
}
}
}
void Foam::fftRenumber
(
List<complex>& data,
const labelList& nn
)
{
List<complex> renumData(data);
label nnprod(1);
forAll(nn, i)
{
nnprod *= nn[i];
}
label ii(0), l1(0), l2(0);
fftRenumberRecurse
(
data,
renumData,
nn,
nnprod,
ii,
l1,
l2
);
}
// ************************************************************************* //
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