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========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Copyright (C) 2011-2021 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
The function renumbers the addressing such that the band of the
matrix is reduced. The algorithm uses a simple search through the
neighbour list
See http://en.wikipedia.org/wiki/Cuthill-McKee_algorithm
\*---------------------------------------------------------------------------*/
#include "bandCompression.H"
#include "SLList.H"
#include "IOstreams.H"
#include "DynamicList.H"
#include "ListOps.H"
#include "PackedBoolList.H"
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Foam::labelList Foam::bandCompression(const labelListList& cellCellAddressing)
{
labelList newOrder(cellCellAddressing.size());
// the business bit of the renumbering
SLList<label> nextCell;
PackedBoolList visited(cellCellAddressing.size());
label cellInOrder = 0;
// Work arrays. Kept outside of loop to minimise allocations.
// - neighbour cells
DynamicList<label> nbrs;
// - corresponding weights
DynamicList<label> weights;
// - ordering
labelList order;
while (true)
{
// For a disconnected region find the lowest connected cell.
label currentCell = -1;
label minWeight = labelMax;
forAll(visited, celli)
{
// find the lowest connected cell that has not been visited yet
if (!visited[celli])
{
if (cellCellAddressing[celli].size() < minWeight)
{
minWeight = cellCellAddressing[celli].size();
currentCell = celli;
}
}
}
if (currentCell == -1)
{
break;
}
// Starting from currentCell walk breadth-first
// use this cell as a start
nextCell.append(currentCell);
// loop through the nextCell list. Add the first cell into the
// cell order if it has not already been visited and ask for its
// neighbours. If the neighbour in question has not been visited,
// add it to the end of the nextCell list
while (nextCell.size())
{
currentCell = nextCell.removeHead();
if (!visited[currentCell])
{
visited[currentCell] = 1;
// add into cellOrder
newOrder[cellInOrder] = currentCell;
cellInOrder++;
// find if the neighbours have been visited
const labelList& neighbours = cellCellAddressing[currentCell];
// Add in increasing order of connectivity
// 1. Count neighbours of unvisited neighbours
nbrs.clear();
weights.clear();
forAll(neighbours, nI)
{
label nbr = neighbours[nI];
if (!visited[nbr])
{
// not visited, add to the list
nbrs.append(nbr);
weights.append(cellCellAddressing[nbr].size());
}
}
// 2. Sort in ascending order
sortedOrder(weights, order);
// 3. Add in sorted order
forAll(order, i)
{
nextCell.append(nbrs[i]);
}
}
}
}
return newOrder;
}
Foam::labelList Foam::bandCompression
(
const labelList& cellCells,
const labelList& offsets
)
{
// Count number of neighbours
labelList numNbrs(offsets.size()-1, 0);
forAll(numNbrs, celli)
{
label start = offsets[celli];
label end = offsets[celli+1];
for (label facei = start; facei < end; facei++)
{
numNbrs[celli]++;
numNbrs[cellCells[facei]]++;
}
}
labelList newOrder(offsets.size()-1);
// the business bit of the renumbering
SLList<label> nextCell;
PackedBoolList visited(offsets.size()-1);
label cellInOrder = 0;
// Work arrays. Kept outside of loop to minimise allocations.
// - neighbour cells
DynamicList<label> nbrs;
// - corresponding weights
DynamicList<label> weights;
// - ordering
labelList order;
while (true)
{
// For a disconnected region find the lowest connected cell.
label currentCell = -1;
label minWeight = labelMax;
forAll(visited, celli)
{
// find the lowest connected cell that has not been visited yet
if (!visited[celli])
{
if (numNbrs[celli] < minWeight)
{
minWeight = numNbrs[celli];
currentCell = celli;
}
}
}
if (currentCell == -1)
{
break;
}
// Starting from currentCell walk breadth-first
// use this cell as a start
nextCell.append(currentCell);
// loop through the nextCell list. Add the first cell into the
// cell order if it has not already been visited and ask for its
// neighbours. If the neighbour in question has not been visited,
// add it to the end of the nextCell list
while (nextCell.size())
{
currentCell = nextCell.removeHead();
if (!visited[currentCell])
{
visited[currentCell] = 1;
// add into cellOrder
newOrder[cellInOrder] = currentCell;
cellInOrder++;
// Add in increasing order of connectivity
// 1. Count neighbours of unvisited neighbours
nbrs.clear();
weights.clear();
label start = offsets[currentCell];
label end = offsets[currentCell+1];
for (label facei = start; facei < end; facei++)
{
label nbr = cellCells[facei];
if (!visited[nbr])
{
// not visited, add to the list
nbrs.append(nbr);
weights.append(numNbrs[nbr]);
}
}
// 2. Sort in ascending order
sortedOrder(weights, order);
// 3. Add in sorted order
forAll(order, i)
{
nextCell.append(nbrs[i]);
}
}
}
}
return newOrder;
}
// ************************************************************************* //
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