From 3540cda2f97c6cd63fcfe79195ccf73f803f936f Mon Sep 17 00:00:00 2001
From: mattijs <mattijs>
Date: Tue, 16 Jul 2013 21:27:05 +0100
Subject: [PATCH] ENH: bandCompression: addressing in losort form

---
 .../meshes/bandCompression/bandCompression.C  | 127 +++++++++++++++++-
 .../meshes/bandCompression/bandCompression.H  |   5 +-
 2 files changed, 130 insertions(+), 2 deletions(-)

diff --git a/src/OpenFOAM/meshes/bandCompression/bandCompression.C b/src/OpenFOAM/meshes/bandCompression/bandCompression.C
index 96da4db0dc..6a74fdf58a 100644
--- a/src/OpenFOAM/meshes/bandCompression/bandCompression.C
+++ b/src/OpenFOAM/meshes/bandCompression/bandCompression.C
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011-2012 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2013 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -146,4 +146,129 @@ Foam::labelList Foam::bandCompression(const labelListList& cellCellAddressing)
 }
 
 
+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;
+}
+
+
 // ************************************************************************* //
diff --git a/src/OpenFOAM/meshes/bandCompression/bandCompression.H b/src/OpenFOAM/meshes/bandCompression/bandCompression.H
index f1506e5dbc..54e51efd39 100644
--- a/src/OpenFOAM/meshes/bandCompression/bandCompression.H
+++ b/src/OpenFOAM/meshes/bandCompression/bandCompression.H
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011-2012 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2013 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -51,6 +51,9 @@ namespace Foam
 //  original)
 labelList bandCompression(const labelListList& addressing);
 
+//- Renumber with addressing in losort form (neighbour + start in neighbour)
+labelList bandCompression(const labelList& cellCells, const labelList& offsets);
+
 } // End namespace Foam
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //