diff --git a/applications/test/checkDecomposePar/Test-checkDecomposePar.C b/applications/test/checkDecomposePar/Test-checkDecomposePar.C
index d664615503..805b57b9ec 100644
--- a/applications/test/checkDecomposePar/Test-checkDecomposePar.C
+++ b/applications/test/checkDecomposePar/Test-checkDecomposePar.C
@@ -100,10 +100,7 @@ int main(int argc, char *argv[])
             const wordList& regions = iter();
             forAll(regions, i)
             {
-                if (!regionNames.found(regions[i]))
-                {
-                    regionNames.append(regions[i]);
-                }
+                regionNames.appendUniq(regions[i]);
             }
         }
         regionDirs = regionNames;
diff --git a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshCalcDualMesh.C b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshCalcDualMesh.C
index 4a548c89ef..14a2f32fd5 100644
--- a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshCalcDualMesh.C
+++ b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshCalcDualMesh.C
@@ -894,15 +894,8 @@ void Foam::conformalVoronoiMesh::checkCellSizing()
             const label faceOwner = pMesh.faceOwner()[facei];
             const label faceNeighbour = pMesh.faceNeighbour()[facei];
 
-            if (!cellsToResizeMap.found(faceOwner))
-            {
-                cellsToResizeMap.insert(faceOwner);
-            }
-
-            if (!cellsToResizeMap.found(faceNeighbour))
-            {
-                cellsToResizeMap.insert(faceNeighbour);
-            }
+            cellsToResizeMap.insert(faceOwner);
+            cellsToResizeMap.insert(faceNeighbour);
         }
 
         cellsToResizeMap += protrudingCells;
diff --git a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C
index 4affaa5758..fa734f5a18 100644
--- a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C
+++ b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012-2016 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -727,11 +727,7 @@ Foam::label Foam::conformalVoronoiMesh::synchroniseSurfaceTrees
             if (nearest.hit() || nearestEdge.hit())
             {
                 nStoppedInsertion++;
-
-                if (!hits[proci].found(peI))
-                {
-                    hits[proci].insert(peI);
-                }
+                hits[proci].insert(peI);
             }
         }
     }
@@ -822,11 +818,7 @@ Foam::label Foam::conformalVoronoiMesh::synchroniseEdgeTrees
 //                    << endl;
 
                 nStoppedInsertion++;
-
-                if (!hits[proci].found(peI))
-                {
-                    hits[proci].insert(peI);
-                }
+                hits[proci].insert(peI);
             }
         }
     }
diff --git a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshI.H b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshI.H
index caac10dbc8..9d71ce889c 100644
--- a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshI.H
+++ b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshI.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012-2015 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -467,15 +468,8 @@ inline Foam::List<Foam::label> Foam::conformalVoronoiMesh::processorsAttached
 
     forAll(c1Procs, aPI)
     {
-        if (!procsAttached.found(c1Procs[aPI]))
-        {
-            procsAttached.append(c1Procs[aPI]);
-        }
-
-        if (!procsAttached.found(c2Procs[aPI]))
-        {
-            procsAttached.append(c2Procs[aPI]);
-        }
+        procsAttached.appendUniq(c1Procs[aPI]);
+        procsAttached.appendUniq(c2Procs[aPI]);
     }
 
     return List<label>(procsAttached);
diff --git a/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.C b/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.C
index 445416cc9e..80ba11fc9c 100644
--- a/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.C
+++ b/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2013-2016 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -36,23 +36,6 @@ namespace Foam
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
-void Foam::shortEdgeFilter2D::addRegion
-(
-    const label regionI,
-    DynamicList<label>& bPointRegions
-) const
-{
-    if (bPointRegions.empty())
-    {
-        bPointRegions.append(regionI);
-    }
-    else if (!bPointRegions.found(regionI))
-    {
-        bPointRegions.append(regionI);
-    }
-}
-
-
 void Foam::shortEdgeFilter2D::assignBoundaryPointRegions
 (
     List<DynamicList<label>>& boundaryPointRegions
@@ -61,13 +44,10 @@ void Foam::shortEdgeFilter2D::assignBoundaryPointRegions
     forAllConstIters(mapEdgesRegion_, iter)
     {
         const edge& e = iter.key();
-        const label& regionI = iter();
+        const label regi = iter.val();
 
-        const label startI = e.start();
-        const label endI = e.end();
-
-        addRegion(regionI, boundaryPointRegions[startI]);
-        addRegion(regionI, boundaryPointRegions[endI]);
+        boundaryPointRegions[e.start()].appendUniq(regi);
+        boundaryPointRegions[e.end()].appendUniq(regi);
     }
 }
 
diff --git a/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.H b/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.H
index 9c0343e5f7..315e459444 100644
--- a/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.H
+++ b/applications/utilities/mesh/generation/foamyMesh/foamyQuadMesh/shortEdgeFilter2D.H
@@ -51,7 +51,7 @@ namespace Foam
 
 class shortEdgeFilter2D
 {
-    // Private data
+    // Private Data
 
         const CV2D& cv2Dmesh_;
 
@@ -72,12 +72,6 @@ class shortEdgeFilter2D
 
     // Private Member Functions
 
-        void addRegion
-        (
-            const label regionI,
-            DynamicList<label>& bPointRegions
-        ) const;
-
         void assignBoundaryPointRegions
         (
             List<DynamicList<label>>& boundaryPointRegions
diff --git a/applications/utilities/mesh/manipulation/polyDualMesh/meshDualiser.C b/applications/utilities/mesh/manipulation/polyDualMesh/meshDualiser.C
index 0abc91fb28..c512857b76 100644
--- a/applications/utilities/mesh/manipulation/polyDualMesh/meshDualiser.C
+++ b/applications/utilities/mesh/manipulation/polyDualMesh/meshDualiser.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -516,9 +516,9 @@ void Foam::meshDualiser::createFacesAroundEdge
             {
                 label startDual = faceToDualPoint_[startFaceLabel];
 
-                if (startDual != -1 && !verts.found(startDual))
+                if (startDual != -1)
                 {
-                    verts.append(startDual);
+                    verts.appendUniq(startDual);
                 }
             }
             break;
diff --git a/src/OSspecific/MSwindows/fileMonitor/fileMonitor.C b/src/OSspecific/MSwindows/fileMonitor/fileMonitor.C
index db66c0c443..2a34a5c42d 100644
--- a/src/OSspecific/MSwindows/fileMonitor/fileMonitor.C
+++ b/src/OSspecific/MSwindows/fileMonitor/fileMonitor.C
@@ -498,10 +498,8 @@ bool Foam::fileMonitor::removeWatch(const label watchFd)
             << watchFile_[watchFd] << endl;
     }
 
-    if (!freeWatchFds_.found(watchFd))
-    {
-        freeWatchFds_.append(watchFd);
-    }
+    freeWatchFds_.appendUniq(watchFd);
+
     return watcher_->removeWatch(watchFd);
 }
 
diff --git a/src/OSspecific/POSIX/fileMonitor/fileMonitor.C b/src/OSspecific/POSIX/fileMonitor/fileMonitor.C
index 19af5b4243..4f9a95b450 100644
--- a/src/OSspecific/POSIX/fileMonitor/fileMonitor.C
+++ b/src/OSspecific/POSIX/fileMonitor/fileMonitor.C
@@ -494,10 +494,8 @@ bool Foam::fileMonitor::removeWatch(const label watchFd)
             << watchFile_[watchFd] << endl;
     }
 
-    if (!freeWatchFds_.found(watchFd))
-    {
-        freeWatchFds_.append(watchFd);
-    }
+    freeWatchFds_.appendUniq(watchFd);
+
     return watcher_->removeWatch(watchFd);
 }
 
diff --git a/src/OpenFOAM/containers/Lists/DynamicList/DynamicList.H b/src/OpenFOAM/containers/Lists/DynamicList/DynamicList.H
index 76670941fe..ae8c61570d 100644
--- a/src/OpenFOAM/containers/Lists/DynamicList/DynamicList.H
+++ b/src/OpenFOAM/containers/Lists/DynamicList/DynamicList.H
@@ -258,6 +258,10 @@ public:
             inline DynamicList<T, SizeMin>&
             append(SortableList<T>&& lst);
 
+            //- Append an element if not already in the list.
+            //  \return the change in list length
+            inline label appendUniq(const T& val);
+
             //- Remove and return the last element. Fatal on an empty list.
             inline T remove();
 
diff --git a/src/OpenFOAM/containers/Lists/DynamicList/DynamicListI.H b/src/OpenFOAM/containers/Lists/DynamicList/DynamicListI.H
index fdab0b30d2..79da196a1e 100644
--- a/src/OpenFOAM/containers/Lists/DynamicList/DynamicListI.H
+++ b/src/OpenFOAM/containers/Lists/DynamicList/DynamicListI.H
@@ -608,6 +608,21 @@ Foam::DynamicList<T, SizeMin>::append
 }
 
 
+template<class T, int SizeMin>
+inline Foam::label Foam::DynamicList<T, SizeMin>::appendUniq(const T& val)
+{
+    if (this->found(val))
+    {
+        return 0;
+    }
+    else
+    {
+        this->append(val);
+        return 1;  // Increased list length by one
+    }
+}
+
+
 template<class T, int SizeMin>
 inline T Foam::DynamicList<T, SizeMin>::remove()
 {
diff --git a/src/OpenFOAM/containers/Lists/List/List.H b/src/OpenFOAM/containers/Lists/List/List.H
index 7dbcd5077c..89bc21a1cf 100644
--- a/src/OpenFOAM/containers/Lists/List/List.H
+++ b/src/OpenFOAM/containers/Lists/List/List.H
@@ -242,6 +242,10 @@ public:
             template<class Addr>
             inline void append(const IndirectListBase<T, Addr>& list);
 
+            //- Append an element if not already in the list.
+            //  \return the change in list length
+            inline label appendUniq(const T& val);
+
             //- Transfer the contents of the argument List into this list
             //- and annul the argument list
             void transfer(List<T>& list);
diff --git a/src/OpenFOAM/containers/Lists/List/ListI.H b/src/OpenFOAM/containers/Lists/List/ListI.H
index 4e499c0f20..e24aa6c486 100644
--- a/src/OpenFOAM/containers/Lists/List/ListI.H
+++ b/src/OpenFOAM/containers/Lists/List/ListI.H
@@ -218,6 +218,21 @@ inline void Foam::List<T>::append(const IndirectListBase<T, Addr>& list)
 }
 
 
+template<class T>
+inline Foam::label Foam::List<T>::appendUniq(const T& val)
+{
+    if (this->found(val))
+    {
+        return 0;
+    }
+    else
+    {
+        this->append(val);
+        return 1;  // Increased list length by one
+    }
+}
+
+
 // * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
 
 template<class T>
diff --git a/src/OpenFOAM/meshes/polyMesh/polyPatches/derived/wall/wallPolyPatch.C b/src/OpenFOAM/meshes/polyMesh/polyPatches/derived/wall/wallPolyPatch.C
index 5036e07540..d556ac044d 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyPatches/derived/wall/wallPolyPatch.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyPatches/derived/wall/wallPolyPatch.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -53,10 +54,7 @@ Foam::wallPolyPatch::wallPolyPatch
     polyPatch(name, size, start, index, bm, patchType)
 {
     //  wall is not constraint type so add wall group explicitly
-    if (!inGroups().found(typeName))
-    {
-        inGroups().append(typeName);
-    }
+    inGroups().appendUniq(typeName);
 }
 
 
@@ -72,10 +70,7 @@ Foam::wallPolyPatch::wallPolyPatch
     polyPatch(name, dict, index, bm, patchType)
 {
     //  wall is not constraint type so add wall group explicitly
-    if (!inGroups().found(typeName))
-    {
-        inGroups().append(typeName);
-    }
+    inGroups().appendUniq(typeName);
 }
 
 
diff --git a/src/OpenFOAM/meshes/polyMesh/polyPatches/polyPatch/polyPatch.C b/src/OpenFOAM/meshes/polyMesh/polyPatches/polyPatch/polyPatch.C
index 6db7dc22fc..39ab12285e 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyPatches/polyPatch/polyPatch.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyPatches/polyPatch/polyPatch.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -100,14 +100,9 @@ Foam::polyPatch::polyPatch
     faceCellsPtr_(nullptr),
     mePtr_(nullptr)
 {
-    if
-    (
-        patchType != word::null
-     && constraintType(patchType)
-     && !inGroups().found(patchType)
-    )
+    if (!patchType.empty() && constraintType(patchType))
     {
-        inGroups().append(patchType);
+        inGroups().appendUniq(patchType);
     }
 }
 
@@ -161,14 +156,9 @@ Foam::polyPatch::polyPatch
     faceCellsPtr_(nullptr),
     mePtr_(nullptr)
 {
-    if
-    (
-        patchType != word::null
-     && constraintType(patchType)
-     && !inGroups().found(patchType)
-    )
+    if (!patchType.empty() && constraintType(patchType))
     {
-        inGroups().append(patchType);
+        inGroups().appendUniq(patchType);
     }
 }
 
diff --git a/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCellEdges.C b/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCellEdges.C
index fbb4bd57d9..7788c1388f 100644
--- a/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCellEdges.C
+++ b/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCellEdges.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -77,13 +78,10 @@ void Foam::primitiveMesh::calcCellEdges() const
 
             const labelList& curEdges = fe[facei];
 
-            forAll(curEdges, edgeI)
+            for (const label edgei : curEdges)
             {
-                if (!curCellEdges.found(curEdges[edgeI]))
-                {
-                    // Add the edge
-                    curCellEdges.append(curEdges[edgeI]);
-                }
+                // Add the edge
+                curCellEdges.appendUniq(edgei);
             }
         }
 
@@ -93,13 +91,10 @@ void Foam::primitiveMesh::calcCellEdges() const
 
             const labelList& curEdges = fe[facei];
 
-            forAll(curEdges, edgeI)
+            for (const label edgei : curEdges)
             {
-                if (!curCellEdges.found(curEdges[edgeI]))
-                {
-                    // add the edge
-                    curCellEdges.append(curEdges[edgeI]);
-                }
+                // Add the edge
+                curCellEdges.appendUniq(edgei);
             }
         }
 
diff --git a/src/Pstream/mpi/UPstream.C b/src/Pstream/mpi/UPstream.C
index c19ee6bad0..7a5332ce81 100644
--- a/src/Pstream/mpi/UPstream.C
+++ b/src/Pstream/mpi/UPstream.C
@@ -305,12 +305,9 @@ bool Foam::UPstream::init(int& argc, char**& argv, const bool needsThread)
         if (Pstream::master())
         {
             DynamicList<word> allWorlds(numprocs);
-            for (const auto& world : worlds)
+            for (const word& world : worlds)
             {
-                if (!allWorlds.found(world))
-                {
-                    allWorlds.append(world);
-                }
+                allWorlds.appendUniq(world);
             }
             allWorlds_ = std::move(allWorlds);
 
diff --git a/src/dynamicFaMesh/interfaceTrackingFvMesh/interfaceTrackingFvMesh.C b/src/dynamicFaMesh/interfaceTrackingFvMesh/interfaceTrackingFvMesh.C
index f89864304a..5eff990577 100644
--- a/src/dynamicFaMesh/interfaceTrackingFvMesh/interfaceTrackingFvMesh.C
+++ b/src/dynamicFaMesh/interfaceTrackingFvMesh/interfaceTrackingFvMesh.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2019 Zeljko Tukovic, FSB Zagreb.
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -1101,10 +1101,7 @@ void Foam::interfaceTrackingFvMesh::correctPointDisplacement
 
                 if (index == -1)
                 {
-                    if (!pointSet.found(curPoint))
-                    {
-                        pointSet.insert(curPoint);
-                    }
+                    pointSet.insert(curPoint);
                 }
             }
         }
@@ -1127,10 +1124,7 @@ void Foam::interfaceTrackingFvMesh::correctPointDisplacement
 
                 if (index != -1)
                 {
-                    if (!faceSet.found(curFace))
-                    {
-                        faceSet.insert(curFace);
-                    }
+                    faceSet.insert(curFace);
                 }
             }
 
@@ -1197,10 +1191,7 @@ void Foam::interfaceTrackingFvMesh::correctPointDisplacement
 
                 if (index != -1)
                 {
-                    if (!faceSet.found(curFace))
-                    {
-                        faceSet.insert(curFace);
-                    }
+                    faceSet.insert(curFace);
                 }
             }
 
diff --git a/src/dynamicMesh/meshCut/cellLooper/geomCellLooper.C b/src/dynamicMesh/meshCut/cellLooper/geomCellLooper.C
index 9a529e961b..245a15cad9 100644
--- a/src/dynamicMesh/meshCut/cellLooper/geomCellLooper.C
+++ b/src/dynamicMesh/meshCut/cellLooper/geomCellLooper.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -290,14 +290,12 @@ bool Foam::geomCellLooper::cut
         // Check distance of endpoints to cutPlane
         //
 
-        if (!checkedPoints.found(e.start()))
+        if (checkedPoints.insert(e.start()))
         {
-            checkedPoints.insert(e.start());
+            const scalar typLen = pointEqualTol_ * minEdgeLen(e.start());
 
-            scalar typStartLen = pointEqualTol_ * minEdgeLen(e.start());
-
-            // Check distance of startPt to plane.
-            if (cutPlane.distance(points[e.start()]) < typStartLen)
+            // Check distance to plane.
+            if (cutPlane.distance(points[e.start()]) < typLen)
             {
                 // Use point.
                 localLoop.append(vertToEVert(e.start()));
@@ -306,14 +304,13 @@ bool Foam::geomCellLooper::cut
                 useStart = true;
             }
         }
-        if (!checkedPoints.found(e.end()))
+
+        if (checkedPoints.insert(e.end()))
         {
-            checkedPoints.insert(e.end());
+            const scalar typLen = pointEqualTol_ * minEdgeLen(e.end());
 
-            scalar typEndLen = pointEqualTol_ * minEdgeLen(e.end());
-
-            // Check distance of endPt to plane.
-            if (cutPlane.distance(points[e.end()]) < typEndLen)
+            // Check distance to plane.
+            if (cutPlane.distance(points[e.end()]) < typLen)
             {
                 // Use point.
                 localLoop.append(vertToEVert(e.end()));
diff --git a/src/dynamicMesh/polyMeshAdder/polyMeshAdder.C b/src/dynamicMesh/polyMeshAdder/polyMeshAdder.C
index 0dfaa92d41..3b4f801a8f 100644
--- a/src/dynamicMesh/polyMeshAdder/polyMeshAdder.C
+++ b/src/dynamicMesh/polyMeshAdder/polyMeshAdder.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019,2021 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -916,10 +916,7 @@ void Foam::polyMeshAdder::mergePointZones
             else if (pointToZone[allPointi] != zoneI)
             {
                 labelList& pZones = addPointToZones[allPointi];
-                if (!pZones.found(zoneI))
-                {
-                    pZones.append(zoneI);
-                }
+                pZones.appendUniq(zoneI);
             }
         }
     }
@@ -942,10 +939,7 @@ void Foam::polyMeshAdder::mergePointZones
             else if (pointToZone[allPointi] != allZoneI)
             {
                 labelList& pZones = addPointToZones[allPointi];
-                if (!pZones.found(allZoneI))
-                {
-                    pZones.append(allZoneI);
-                }
+                pZones.appendUniq(allZoneI);
             }
         }
     }
@@ -1074,9 +1068,8 @@ void Foam::polyMeshAdder::mergeFaceZones
                     labelList& fZones = addFaceToZones[allFacei];
                     boolList& flipZones = addFaceToFlips[allFacei];
 
-                    if (!fZones.found(zoneI))
+                    if (fZones.appendUniq(zoneI))
                     {
-                        fZones.append(zoneI);
                         flipZones.append(flip0);
                     }
                 }
@@ -1117,9 +1110,8 @@ void Foam::polyMeshAdder::mergeFaceZones
                     labelList& fZones = addFaceToZones[allFacei];
                     boolList& flipZones = addFaceToFlips[allFacei];
 
-                    if (!fZones.found(allZoneI))
+                    if (fZones.appendUniq(allZoneI))
                     {
-                        fZones.append(allZoneI);
                         flipZones.append(flip1);
                     }
                 }
@@ -1239,10 +1231,7 @@ void Foam::polyMeshAdder::mergeCellZones
             else if (cellToZone[cell0] != zoneI)
             {
                 labelList& cZones = addCellToZones[cell0];
-                if (!cZones.found(zoneI))
-                {
-                    cZones.append(zoneI);
-                }
+                cZones.appendUniq(zoneI);
             }
         }
     }
@@ -1264,10 +1253,7 @@ void Foam::polyMeshAdder::mergeCellZones
             else if (cellToZone[allCelli] != allZoneI)
             {
                 labelList& cZones = addCellToZones[allCelli];
-                if (!cZones.found(allZoneI))
-                {
-                    cZones.append(allZoneI);
-                }
+                cZones.appendUniq(allZoneI);
             }
         }
     }
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/combineFaces.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/combineFaces.C
index 440fccfd22..02517d8f49 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/combineFaces.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/combineFaces.C
@@ -267,10 +267,7 @@ bool Foam::combineFaces::faceNeighboursValid
                 }
                 else
                 {
-                    if (!neighbourFaces.found(nbrI))
-                    {
-                        neighbourFaces.append(nbrI);
-                    }
+                    neighbourFaces.appendUniq(nbrI);
                 }
             }
 
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
index 8d2860adbe..f6a9420df9 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
@@ -1849,17 +1849,14 @@ bool Foam::hexRef8::matchHexShape
                         if (iter.found())
                         {
                             labelList& pFaces = iter.val();
-                            if (!pFaces.found(facei))
-                            {
-                                pFaces.append(facei);
-                            }
+                            pFaces.appendUniq(facei);
                         }
                         else
                         {
                             pointFaces.insert
                             (
                                 pointi,
-                                labelList(1, facei)
+                                labelList(one{}, facei)
                             );
                         }
                     }
diff --git a/src/dynamicMesh/slidingInterface/enrichedPatch/enrichedPatchPointPoints.C b/src/dynamicMesh/slidingInterface/enrichedPatch/enrichedPatchPointPoints.C
index bd0736cbe4..3362ec1640 100644
--- a/src/dynamicMesh/slidingInterface/enrichedPatch/enrichedPatchPointPoints.C
+++ b/src/dynamicMesh/slidingInterface/enrichedPatch/enrichedPatchPointPoints.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -58,19 +58,11 @@ void Foam::enrichedPatch::calcPointPoints() const
 
             // Do next label
             const label next = curFace.nextLabel(pointi);
-
-            if (!curPp.found(next))
-            {
-                curPp.append(next);
-            }
+            curPp.appendUniq(next);
 
             // Do previous label
             const label prev = curFace.prevLabel(pointi);
-
-            if (!curPp.found(prev))
-            {
-                curPp.append(prev);
-            }
+            curPp.appendUniq(prev);
         }
     }
 
diff --git a/src/finiteArea/faMesh/faMeshDemandDrivenData.C b/src/finiteArea/faMesh/faMeshDemandDrivenData.C
index 8e9a50dd09..7a363fd2ab 100644
--- a/src/finiteArea/faMesh/faMeshDemandDrivenData.C
+++ b/src/finiteArea/faMesh/faMeshDemandDrivenData.C
@@ -945,7 +945,7 @@ void Foam::faMesh::calcPointAreaNormals() const
 
         labelList curPointPoints = curPatch.edgeLoops()[0];
 
-        for (int i = 0; i < curPointPoints.size(); ++i)
+        for (label i = 0; i < curPointPoints.size(); ++i)
         {
             vector d1 =
                 points[curPatch.meshPoints()[curPointPoints[i]]]
@@ -1212,60 +1212,35 @@ void Foam::faMesh::calcPointAreaNormalsByQuadricsFit() const
 
         labelHashSet pointSet;
 
-        pointSet.insert(curPoint);
-        for (label i=0; i<curFaces.size(); ++i)
+        for (const label facei : curFaces)
         {
-            const labelList& facePoints = faces[curFaces[i]];
-            for (label j=0; j<facePoints.size(); ++j)
-            {
-                if (!pointSet.found(facePoints[j]))
-                {
-                    pointSet.insert(facePoints[j]);
-                }
-            }
+            const labelList& facePoints = faces[facei];
+            pointSet.insert(facePoints);
         }
         pointSet.erase(curPoint);
         labelList curPoints(pointSet.toc());
 
-        if (curPoints.size() < 5)
+        if (pointSet.size() < 5)
         {
             DebugInfo
                 << "WARNING: Extending point set for fitting." << endl;
 
             labelHashSet faceSet(pointFaces[curPoint]);
             labelList curFaces(faceSet.toc());
-            forAll(curFaces, faceI)
+            for (const label facei : curFaces)
             {
-                const labelList& curFaceFaces =
-                    patch().faceFaces()[curFaces[faceI]];
-
-                forAll(curFaceFaces, fI)
-                {
-                    label curFaceFace = curFaceFaces[fI];
-
-                    if (!faceSet.found(curFaceFace))
-                    {
-                        faceSet.insert(curFaceFace);
-                    }
-                }
+                const labelList& curFaceFaces = patch().faceFaces()[facei];
+                faceSet.insert(curFaceFaces);
             }
             curFaces = faceSet.toc();
 
-            labelHashSet pointSet;
+            pointSet.clear();
 
-            pointSet.insert(curPoint);
-            for (label i=0; i<curFaces.size(); ++i)
+            for (const label facei : curFaces)
             {
-                const labelList& facePoints = faces[curFaces[i]];
-                for (label j=0; j<facePoints.size(); ++j)
-                {
-                    if (!pointSet.found(facePoints[j]))
-                    {
-                        pointSet.insert(facePoints[j]);
-                    }
-                }
+                const labelList& facePoints = faces[facei];
+                pointSet.insert(facePoints);
             }
-
             pointSet.erase(curPoint);
             curPoints = pointSet.toc();
         }
@@ -1372,17 +1347,10 @@ void Foam::faMesh::calcPointAreaNormalsByQuadricsFit() const
 
                 labelHashSet pointSet;
 
-                pointSet.insert(curPoint);
-                for (label i=0; i<curFaces.size(); ++i)
+                for (const label facei : curFaces)
                 {
-                    const labelList& facePoints = faces[curFaces[i]];
-                    for (label j=0; j<facePoints.size(); ++j)
-                    {
-                        if (!pointSet.found(facePoints[j]))
-                        {
-                            pointSet.insert(facePoints[j]);
-                        }
-                    }
+                    const labelList& facePoints = faces[facei];
+                    pointSet.insert(facePoints);
                 }
                 pointSet.erase(curPoint);
                 labelList curPoints = pointSet.toc();
@@ -1456,17 +1424,10 @@ void Foam::faMesh::calcPointAreaNormalsByQuadricsFit() const
 
                 labelHashSet pointSet;
 
-                pointSet.insert(curPoint);
-                for (label i=0; i<curFaces.size(); ++i)
+                for (const label facei : curFaces)
                 {
-                    const labelList& facePoints = faces[curFaces[i]];
-                    for (label j=0; j<facePoints.size(); ++j)
-                    {
-                        if (!pointSet.found(facePoints[j]))
-                        {
-                            pointSet.insert(facePoints[j]);
-                        }
-                    }
+                    const labelList& facePoints = faces[facei];
+                    pointSet.insert(facePoints);
                 }
                 pointSet.erase(curPoint);
                 labelList curPoints = pointSet.toc();
@@ -1653,17 +1614,10 @@ void Foam::faMesh::calcPointAreaNormalsByQuadricsFit() const
                 const labelList curFaces(faceSet.toc());
 
                 labelHashSet pointSet;
-                pointSet.insert(curPoint);
-                for (label i=0; i<curFaces.size(); ++i)
+                for (const label facei : curFaces)
                 {
-                    const labelList& facePoints = faces[curFaces[i]];
-                    for (label j=0; j<facePoints.size(); ++j)
-                    {
-                        if (!pointSet.found(facePoints[j]))
-                        {
-                            pointSet.insert(facePoints[j]);
-                        }
-                    }
+                    const labelList& facePoints = faces[facei];
+                    pointSet.insert(facePoints);
                 }
                 pointSet.erase(curPoint);
                 labelList curPoints = pointSet.toc();
diff --git a/src/finiteVolume/fvMesh/extendedStencil/faceToCell/globalIndexStencils/CFCFaceToCellStencil.C b/src/finiteVolume/fvMesh/extendedStencil/faceToCell/globalIndexStencils/CFCFaceToCellStencil.C
index 1cd27154f4..8783179386 100644
--- a/src/finiteVolume/fvMesh/extendedStencil/faceToCell/globalIndexStencils/CFCFaceToCellStencil.C
+++ b/src/finiteVolume/fvMesh/extendedStencil/faceToCell/globalIndexStencils/CFCFaceToCellStencil.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -140,10 +141,8 @@ void Foam::CFCFaceToCellStencil::calcCellStencil
         allGlobalFaces.clear();
 
         // My faces first
-        forAll(cFaces, i)
+        for (const label facei : cFaces)
         {
-            label facei = cFaces[i];
-
             if
             (
                 mesh().isInternalFace(facei)
@@ -155,10 +154,8 @@ void Foam::CFCFaceToCellStencil::calcCellStencil
         }
 
         // faces of neighbouring cells second
-        forAll(cFaces, i)
+        for (const label facei : cFaces)
         {
-            label facei = cFaces[i];
-
             if (mesh().isInternalFace(facei))
             {
                 label nbrCelli = own[facei];
@@ -168,23 +165,18 @@ void Foam::CFCFaceToCellStencil::calcCellStencil
                 }
                 const cell& nbrFaces = mesh().cells()[nbrCelli];
 
-                forAll(nbrFaces, j)
+                for (const label nbrFacei : nbrFaces)
                 {
-                    label nbrFacei = nbrFaces[j];
-
                     if
                     (
                         mesh().isInternalFace(nbrFacei)
                      || validBFace[nbrFacei-mesh().nInternalFaces()]
                     )
                     {
-                        label nbrGlobalI = globalNumbering().toGlobal(nbrFacei);
+                        label nbrGlobali = globalNumbering().toGlobal(nbrFacei);
 
-                        // Check if already there. Note:should use hashset?
-                        if (!allGlobalFaces.found(nbrGlobalI))
-                        {
-                            allGlobalFaces.append(nbrGlobalI);
-                        }
+                        // Note:should use hashset?
+                        allGlobalFaces.appendUniq(nbrGlobali);
                     }
                 }
             }
@@ -193,15 +185,10 @@ void Foam::CFCFaceToCellStencil::calcCellStencil
                 const labelList& nbrGlobalFaces =
                     neiGlobal[facei-mesh().nInternalFaces()];
 
-                forAll(nbrGlobalFaces, j)
+                for (const label nbrGlobali : nbrGlobalFaces)
                 {
-                    label nbrGlobalI = nbrGlobalFaces[j];
-
-                    // Check if already there. Note:should use hashset?
-                    if (!allGlobalFaces.found(nbrGlobalI))
-                    {
-                        allGlobalFaces.append(nbrGlobalI);
-                    }
+                    // Note:should use hashset?
+                    allGlobalFaces.appendUniq(nbrGlobali);
                 }
             }
         }
diff --git a/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyLayerDriver.C b/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyLayerDriver.C
index 2bd3c71bc7..63e68240e7 100644
--- a/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyLayerDriver.C
+++ b/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyLayerDriver.C
@@ -1974,14 +1974,11 @@ void Foam::snappyLayerDriver::getPatchDisplacement
 //                if (faceFnd.found())
 //                {
 //                    labelList& faces = faceFnd();
-//                    if (!faces.found(patchFacei))
-//                    {
-//                        faces.append(patchFacei);
-//                    }
+//                    faces.appendUniq(patchFacei);
 //                }
 //                else
 //                {
-//                    cellToFaces.insert(celli, labelList(1, patchFacei));
+//                    cellToFaces.insert(celli, labelList(one{}, patchFacei));
 //                }
 //            }
 //
diff --git a/src/meshTools/cellDist/cellDistFuncs.C b/src/meshTools/cellDist/cellDistFuncs.C
index f625707f06..29bb06a81b 100644
--- a/src/meshTools/cellDist/cellDistFuncs.C
+++ b/src/meshTools/cellDist/cellDistFuncs.C
@@ -107,10 +107,7 @@ void Foam::cellDistFuncs::getPointNeighbours
 
     for (const label nbr : faceNeighbours)
     {
-        if (!neighbours.found(nbr))
-        {
-            neighbours.append(nbr);
-        }
+        neighbours.appendUniq(nbr);
     }
 
     // Add all point-only neighbours by linear searching in edge neighbours.
@@ -128,10 +125,7 @@ void Foam::cellDistFuncs::getPointNeighbours
         for (const label facei : pointNbs)
         {
             // Check for facei in edge-neighbours part of neighbours
-            if (!neighbours.found(facei))
-            {
-                neighbours.append(facei);
-            }
+            neighbours.appendUniq(facei);
         }
     }
 
diff --git a/src/meshTools/cellFeatures/cellFeatures.C b/src/meshTools/cellFeatures/cellFeatures.C
index 098907fc87..3d00718efa 100644
--- a/src/meshTools/cellFeatures/cellFeatures.C
+++ b/src/meshTools/cellFeatures/cellFeatures.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -180,16 +180,12 @@ void Foam::cellFeatures::walkSuperFace
     Map<label>& toSuperFace
 ) const
 {
-    if (!toSuperFace.found(facei))
+    if (toSuperFace.insert(facei, superFacei))
     {
-        toSuperFace.insert(facei, superFacei);
-
         const labelList& fEdges = mesh_.faceEdges()[facei];
 
-        forAll(fEdges, fEdgeI)
+        for (const label edgeI : fEdges)
         {
-            label edgeI = fEdges[fEdgeI];
-
             if (!featureEdge_.found(edgeI))
             {
                 label face0;
diff --git a/src/meshTools/mappedPatches/mappedPolyPatch/mappedPolyPatch.C b/src/meshTools/mappedPatches/mappedPolyPatch/mappedPolyPatch.C
index 18d8e7f776..933d9a88ed 100644
--- a/src/meshTools/mappedPatches/mappedPolyPatch/mappedPolyPatch.C
+++ b/src/meshTools/mappedPatches/mappedPolyPatch/mappedPolyPatch.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -55,10 +56,7 @@ Foam::mappedPolyPatch::mappedPolyPatch
     mappedPatchBase(static_cast<const polyPatch&>(*this))
 {
     //  mapped is not constraint type so add mapped group explicitly
-    if (!inGroups().found(typeName))
-    {
-        inGroups().append(typeName);
-    }
+    inGroups().appendUniq(typeName);
 }
 
 
@@ -125,10 +123,7 @@ Foam::mappedPolyPatch::mappedPolyPatch
     mappedPatchBase(*this, dict)
 {
     //  mapped is not constraint type so add mapped group explicitly
-    if (!inGroups().found(typeName))
-    {
-        inGroups().append(typeName);
-    }
+    inGroups().appendUniq(typeName);
 }
 
 
diff --git a/src/meshTools/mappedPatches/mappedPolyPatch/mappedWallPolyPatch.C b/src/meshTools/mappedPatches/mappedPolyPatch/mappedWallPolyPatch.C
index 5a22fc5b01..6a8f11745e 100644
--- a/src/meshTools/mappedPatches/mappedPolyPatch/mappedWallPolyPatch.C
+++ b/src/meshTools/mappedPatches/mappedPolyPatch/mappedWallPolyPatch.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -61,10 +62,7 @@ Foam::mappedWallPolyPatch::mappedWallPolyPatch
     mappedPatchBase(static_cast<const polyPatch&>(*this))
 {
     //  mapped is not constraint type so add mapped group explicitly
-    if (!inGroups().found(mappedPolyPatch::typeName))
-    {
-        inGroups().append(mappedPolyPatch::typeName);
-    }
+    inGroups().appendUniq(mappedPolyPatch::typeName);
 }
 
 
@@ -131,10 +129,7 @@ Foam::mappedWallPolyPatch::mappedWallPolyPatch
     mappedPatchBase(*this, dict)
 {
     //  mapped is not constraint type so add mapped group explicitly
-    if (!inGroups().found(mappedPolyPatch::typeName))
-    {
-        inGroups().append(mappedPolyPatch::typeName);
-    }
+    inGroups().appendUniq(mappedPolyPatch::typeName);
 }
 
 
diff --git a/src/meshTools/regionSplit/localPointRegion.C b/src/meshTools/regionSplit/localPointRegion.C
index ac5453ba75..5a326c2ae9 100644
--- a/src/meshTools/regionSplit/localPointRegion.C
+++ b/src/meshTools/regionSplit/localPointRegion.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2015 OpenCFD Ltd.
+    Copyright (C) 2015-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -172,7 +172,7 @@ void Foam::localPointRegion::countPointRegions
                         }
                         else
                         {
-                            label localPointi = meshPointMap_.size();
+                            const label localPointi = meshPointMap_.size();
                             meshPointMap_.insert(pointi, localPointi);
                             labelList regions(2);
                             regions[0] = minPointRegion[pointi];
@@ -180,7 +180,7 @@ void Foam::localPointRegion::countPointRegions
                             pointRegions.append(regions);
                         }
 
-                        label meshFaceMapI = meshFaceMap_.size();
+                        const label meshFaceMapI = meshFaceMap_.size();
                         meshFaceMap_.insert(facei, meshFaceMapI);
                     }
                 }
@@ -372,7 +372,7 @@ void Foam::localPointRegion::calcPointRegions
                         const label pointi = f[fp];
                         auto iter = minPointValue.find(pointi);
 
-                        if (iter == minPointValue.end())
+                        if (!iter.found())
                         {
                             minPointValue.insert(pointi, minRegion[facei][fp]);
                         }
diff --git a/src/overset/oversetPolyPatch/oversetPolyPatch.C b/src/overset/oversetPolyPatch/oversetPolyPatch.C
index 71b9877f26..cb3893bdf0 100644
--- a/src/overset/oversetPolyPatch/oversetPolyPatch.C
+++ b/src/overset/oversetPolyPatch/oversetPolyPatch.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2017 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -56,10 +56,7 @@ Foam::oversetPolyPatch::oversetPolyPatch
     masterPatchID_(-1)
 {
     //  'overset' is not constraint type so add to group explicitly
-    if (!inGroups().found(typeName))
-    {
-        inGroups().append(typeName);
-    }
+    inGroups().appendUniq(typeName);
 }
 
 
@@ -76,10 +73,7 @@ Foam::oversetPolyPatch::oversetPolyPatch
     masterPatchID_(-1)
 {
     //  'overset' is not constraint type so add to group explicitly
-    if (!inGroups().found(typeName))
-    {
-        inGroups().append(typeName);
-    }
+    inGroups().appendUniq(typeName);
 }
 
 
diff --git a/src/sampling/meshToMesh/calcMethod/mapNearest/mapNearestMethod.C b/src/sampling/meshToMesh/calcMethod/mapNearest/mapNearestMethod.C
index c128db7d59..679c8c022f 100644
--- a/src/sampling/meshToMesh/calcMethod/mapNearest/mapNearestMethod.C
+++ b/src/sampling/meshToMesh/calcMethod/mapNearest/mapNearestMethod.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2013-2016 OpenFOAM Foundation
-    Copyright (C) 2015 OpenCFD Ltd.
+    Copyright (C) 2015-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -290,8 +290,8 @@ Foam::label Foam::mapNearestMethod::findMappedSrcCell
     const List<DynamicList<label>>& tgtToSrc
 ) const
 {
-    DynamicList<label> testCells(10);
-    DynamicList<label> visitedCells(10);
+    DynamicList<label> testCells(16);
+    DynamicList<label> visitedCells(16);
 
     testCells.append(tgtCelli);
 
@@ -312,11 +312,11 @@ Foam::label Foam::mapNearestMethod::findMappedSrcCell
             {
                 const labelList& nbrCells = tgt_.cellCells()[tgtI];
 
-                forAll(nbrCells, i)
+                for (const label nbrCelli : nbrCells)
                 {
-                    if (!visitedCells.found(nbrCells[i]))
+                    if (!visitedCells.found(nbrCelli))
                     {
-                        testCells.append(nbrCells[i]);
+                        testCells.append(nbrCelli);
                     }
                 }
             }
diff --git a/src/sampling/meshToMesh/calcMethod/meshToMeshMethod/meshToMeshMethod.C b/src/sampling/meshToMesh/calcMethod/meshToMeshMethod/meshToMeshMethod.C
index e2bdc189c0..bf879b9c70 100644
--- a/src/sampling/meshToMesh/calcMethod/meshToMeshMethod/meshToMeshMethod.C
+++ b/src/sampling/meshToMesh/calcMethod/meshToMeshMethod/meshToMeshMethod.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2013-2014 OpenFOAM Foundation
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -194,13 +194,9 @@ void Foam::meshToMeshMethod::appendNbrCells
     // filter out cells already visited from cell neighbours
     for (const label nbrCelli : nbrCells)
     {
-        if
-        (
-            !visitedCells.found(nbrCelli)
-         && !nbrCellIDs.found(nbrCelli)
-        )
+        if (!visitedCells.found(nbrCelli))
         {
-            nbrCellIDs.append(nbrCelli);
+            nbrCellIDs.appendUniq(nbrCelli);
         }
     }
 }
diff --git a/src/thermophysicalModels/reactionThermo/chemistryReaders/chemkinReader/chemkinLexer.L b/src/thermophysicalModels/reactionThermo/chemistryReaders/chemkinReader/chemkinLexer.L
index a117a58a85..cf3ef8f3f3 100644
--- a/src/thermophysicalModels/reactionThermo/chemistryReaders/chemkinReader/chemkinLexer.L
+++ b/src/thermophysicalModels/reactionThermo/chemistryReaders/chemkinReader/chemkinLexer.L
@@ -270,8 +270,6 @@ scalar RRreaction = RRcal;
 scalar allCommonT = 1000.0;
 
 word currentElementName;
-label currentElementIndex = 0;
-
 word currentSpecieName;
 label currentSpecieIndex = 0;
 label nSpecieElements = 0;
@@ -332,9 +330,8 @@ bool finishReaction = false;
         currentElementName = word::validate(YYText());
         correctElementName(currentElementName);
 
-        if (!elementIndices_.found(currentElementName))
+        if (elementIndices_.insert(currentElementName, elementNames_.size()))
         {
-            elementIndices_.insert(currentElementName, currentElementIndex++);
             elementNames_.append(currentElementName);
         }
         else
diff --git a/src/thermophysicalModels/reactionThermo/chemistryReaders/foamChemistryReader/foamChemistryReader.C b/src/thermophysicalModels/reactionThermo/chemistryReaders/foamChemistryReader/foamChemistryReader.C
index 95163ebe4a..db068fe133 100644
--- a/src/thermophysicalModels/reactionThermo/chemistryReaders/foamChemistryReader/foamChemistryReader.C
+++ b/src/thermophysicalModels/reactionThermo/chemistryReaders/foamChemistryReader/foamChemistryReader.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -61,9 +61,8 @@ void Foam::foamChemistryReader<ThermoType>::readSpeciesComposition()
 
     for (const word& elemName : elems)
     {
-        if (!elementIndices_.found(elemName))
+        if (elementIndices_.insert(elemName, elementNames_.size()))
         {
-            elementIndices_.insert(elemName, elementNames_.size());
             elementNames_.append(elemName);
         }
         else