diff --git a/applications/utilities/mesh/advanced/modifyMesh/cellSplitter.C b/applications/utilities/mesh/advanced/modifyMesh/cellSplitter.C
index 037e3a18b2..356617bd60 100644
--- a/applications/utilities/mesh/advanced/modifyMesh/cellSplitter.C
+++ b/applications/utilities/mesh/advanced/modifyMesh/cellSplitter.C
@@ -148,7 +148,7 @@ void Foam::cellSplitter::setRefinement
 )
 {
     addedPoints_.clear();
-    addedPoints_.resize(cellToMidPoint.size());
+    addedPoints_.reserve(cellToMidPoint.size());
 
 
     //
@@ -184,7 +184,7 @@ void Foam::cellSplitter::setRefinement
     // Add cells (first one is modified original cell)
     //
 
-    Map<labelList> cellToCells(cellToMidPoint.size());
+    Map<labelList> cellToCells(2*cellToMidPoint.size());
 
     forAllConstIters(cellToMidPoint, iter)
     {
diff --git a/applications/utilities/mesh/conversion/ensightToFoam/ensightMeshReader.C b/applications/utilities/mesh/conversion/ensightToFoam/ensightMeshReader.C
index 39c0f2e7e6..91be645d68 100644
--- a/applications/utilities/mesh/conversion/ensightToFoam/ensightMeshReader.C
+++ b/applications/utilities/mesh/conversion/ensightToFoam/ensightMeshReader.C
@@ -102,7 +102,7 @@ void Foam::fileFormats::ensightMeshReader::readIDs
     foamToElem.resize(sz+nShapes);
     if (doRead)
     {
-        elemToFoam.resize(sz+nShapes);
+        elemToFoam.reserve(elemToFoam.size()+nShapes);
         for (label shapei = 0; shapei < nShapes; shapei++)
         {
             label elemi;
diff --git a/applications/utilities/mesh/conversion/fluent3DMeshToFoam/fluent3DMeshToFoam.L b/applications/utilities/mesh/conversion/fluent3DMeshToFoam/fluent3DMeshToFoam.L
index 0fdc03b2c7..f46d9c2b86 100644
--- a/applications/utilities/mesh/conversion/fluent3DMeshToFoam/fluent3DMeshToFoam.L
+++ b/applications/utilities/mesh/conversion/fluent3DMeshToFoam/fluent3DMeshToFoam.L
@@ -76,14 +76,14 @@ label nCells = 0;
 
 bool hangingNodes = false;
 
-pointField points(0);
-faceList faces(0);
-labelList owner(0);
-labelList neighbour(0);
+pointField points;
+faceList faces;
+labelList owner;
+labelList neighbour;
 
 // Group type and name
-Map<word> groupType(128);
-Map<word> groupName(128);
+Map<word> groupType;
+Map<word> groupName;
 
 // Point groups
 DynamicList<label> pointGroupZoneID;
diff --git a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/DelaunayMesh/DelaunayMeshIO.C b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/DelaunayMesh/DelaunayMeshIO.C
index 4f73231286..320f442a97 100644
--- a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/DelaunayMesh/DelaunayMeshIO.C
+++ b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/DelaunayMesh/DelaunayMeshIO.C
@@ -357,7 +357,7 @@ Foam::DelaunayMesh<Triangulation>::createMesh
     List<DynamicList<face>> patchFaces(1, DynamicList<face>());
     List<DynamicList<label>> patchOwners(1, DynamicList<label>());
 
-    vertexMap.resize(vertexCount());
+    vertexMap.reserve(vertexCount());
     cellMap.setSize(Triangulation::number_of_finite_cells(), -1);
 
     // Calculate pts and a map of point index to location in pts.
diff --git a/applications/utilities/mesh/manipulation/checkMesh/checkGeometry.C b/applications/utilities/mesh/manipulation/checkMesh/checkGeometry.C
index 482acaaff3..b8008a71b4 100644
--- a/applications/utilities/mesh/manipulation/checkMesh/checkGeometry.C
+++ b/applications/utilities/mesh/manipulation/checkMesh/checkGeometry.C
@@ -240,13 +240,13 @@ bool Foam::checkWedges
 
         if (setPtr)
         {
-            setPtr->resize(2*nEdgesInError);
+            setPtr->reserve(2*nEdgesInError);
             forAllConstIters(edgesInError, iter)
             {
-                if (iter() >= 0)
+                if (iter.val() >= 0)
                 {
-                    setPtr->insert(iter.key()[0]);
-                    setPtr->insert(iter.key()[1]);
+                    setPtr->insert(iter.key().first());
+                    setPtr->insert(iter.key().second());
                 }
             }
         }
diff --git a/applications/utilities/mesh/manipulation/setSet/setSet.C b/applications/utilities/mesh/manipulation/setSet/setSet.C
index b717e9f152..af462ed6d9 100644
--- a/applications/utilities/mesh/manipulation/setSet/setSet.C
+++ b/applications/utilities/mesh/manipulation/setSet/setSet.C
@@ -375,7 +375,7 @@ bool doCommand
 
                 topoSet& currentSet = currentSetPtr();
                 // Presize it according to current mesh data.
-                currentSet.resize(max(currentSet.size(), typSize));
+                currentSet.reserve(max(currentSet.size(), typSize));
             }
         }
 
diff --git a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C
index f60afd763f..670ff7d845 100644
--- a/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C
+++ b/src/OpenFOAM/algorithms/dynamicIndexedOctree/dynamicIndexedOctree.C
@@ -2164,12 +2164,9 @@ Foam::label Foam::dynamicIndexedOctree<Type>::findBox
 
     if (!nodes_.empty())
     {
-        if (!elements.capacity())
-        {
-            // Some arbitrary minimal size estimate (eg, 1/100 are found)
-            label estimatedCapacity(max(256, 2*(shapes_.size() / 100)));
-            elements.resize(estimatedCapacity);
-        }
+        // Some arbitrary minimal size estimate (eg, 1/100 are found)
+        label estimatedCount(max(128, (shapes_.size() / 100)));
+        elements.reserve(estimatedCount);
 
         // start node=0, store results
         findBox(0, searchBox, &elements);
@@ -2223,12 +2220,9 @@ Foam::label Foam::dynamicIndexedOctree<Type>::findSphere
 
     if (!nodes_.empty())
     {
-        if (!elements.capacity())
-        {
-            // Some arbitrary minimal size estimate (eg, 1/100 are found)
-            label estimatedCapacity(max(256, 2*(shapes_.size()/100)));
-            elements.resize(estimatedCapacity);
-        }
+        // Some arbitrary minimal size estimate (eg, 1/100 are found)
+        label estimatedCount(max(128, (shapes_.size() / 100)));
+        elements.reserve(estimatedCount);
 
         // start node=0, store results
         findSphere(0, centre, radiusSqr, &elements);
diff --git a/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C b/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C
index b75d9dfbf5..590cea90db 100644
--- a/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C
+++ b/src/OpenFOAM/algorithms/indexedOctree/indexedOctree.C
@@ -2517,12 +2517,9 @@ Foam::label Foam::indexedOctree<Type>::findBox
 
     if (!nodes_.empty())
     {
-        if (!elements.capacity())
-        {
-            // Some arbitrary minimal size estimate (eg, 1/100 are found)
-            label estimatedCapacity(max(256, 2*(shapes_.size() / 100)));
-            elements.resize(estimatedCapacity);
-        }
+        // Some arbitrary minimal size estimate (eg, 1/100 are found)
+        label estimatedCount(max(128, (shapes_.size() / 100)));
+        elements.reserve(estimatedCount);
 
         // start node=0, store results
         findBox(0, searchBox, &elements);
@@ -2576,12 +2573,9 @@ Foam::label Foam::indexedOctree<Type>::findSphere
 
     if (!nodes_.empty())
     {
-        if (!elements.capacity())
-        {
-            // Some arbitrary minimal size estimate (eg, 1/100 are found)
-            label estimatedCapacity(max(256, 2*(shapes_.size() / 100)));
-            elements.resize(estimatedCapacity);
-        }
+        // Some arbitrary minimal size estimate (eg, 1/100 are found)
+        label estimatedCount(max(128, (shapes_.size() / 100)));
+        elements.reserve(estimatedCount);
 
         // start node=0, store results
         findSphere(0, centre, radiusSqr, &elements);
diff --git a/src/OpenFOAM/expressions/exprDriver/exprDriverFunctions.C b/src/OpenFOAM/expressions/exprDriver/exprDriverFunctions.C
index 0df7706169..f1d0096a15 100644
--- a/src/OpenFOAM/expressions/exprDriver/exprDriverFunctions.C
+++ b/src/OpenFOAM/expressions/exprDriver/exprDriverFunctions.C
@@ -43,6 +43,7 @@ static wordHashSet getAcceptableFunctionKeys
 )
 {
     wordHashSet acceptKeys(0);
+    wordHashSet rejectKeys(0);
 
     if (!dictPtr)
     {
@@ -51,8 +52,8 @@ static wordHashSet getAcceptableFunctionKeys
 
     const dictionary& dict = *dictPtr;
 
-    acceptKeys.resize(2*dict.size());
-    wordHashSet rejectKeys(2*dict.size());
+    acceptKeys.reserve(dict.size());
+    rejectKeys.reserve(dict.size());
 
     for (const entry& dEntry : dict)
     {
diff --git a/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalPoints.C b/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalPoints.C
index de0b3210c7..25ce60d1c8 100644
--- a/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalPoints.C
+++ b/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalPoints.C
@@ -768,7 +768,7 @@ void Foam::globalPoints::remove
 
     // Save old ones.
     Map<label> oldMeshToProcPoint(std::move(meshToProcPoint_));
-    meshToProcPoint_.resize(oldMeshToProcPoint.size());
+    meshToProcPoint_.reserve(oldMeshToProcPoint.size());
     DynamicList<labelPairList> oldProcPoints(std::move(procPoints_));
     procPoints_.setCapacity(oldProcPoints.size());
 
@@ -867,7 +867,7 @@ void Foam::globalPoints::remove
     }
 
     procPoints_.shrink();
-    meshToProcPoint_.resize(2*procPoints_.size());
+    meshToProcPoint_.reserve(procPoints_.size());
 }
 
 
diff --git a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.C b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.C
index 6fc781028b..b8efeb9be7 100644
--- a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.C
+++ b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.C
@@ -413,7 +413,7 @@ void Foam::mapDistributeBase::calcCompactAddressing
         compactMap[proci].clear();
         if (proci != myRank)
         {
-            compactMap[proci].resize(2*nNonLocal[proci]);
+            compactMap[proci].reserve(nNonLocal[proci]);
         }
     }
 
@@ -464,7 +464,7 @@ void Foam::mapDistributeBase::calcCompactAddressing
         compactMap[proci].clear();
         if (proci != myRank)
         {
-            compactMap[proci].resize(2*nNonLocal[proci]);
+            compactMap[proci].reserve(nNonLocal[proci]);
         }
     }
 
diff --git a/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C b/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
index 21f4a2506c..29ffe6f3f1 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
@@ -742,7 +742,7 @@ Foam::labelList Foam::polyBoundaryMesh::indices
     // Only check groups if requested and they exist
     if (useGroups && this->hasGroupIDs())
     {
-        ids.resize(2*this->size());
+        ids.reserve(this->size());
 
         const auto& groupLookup = groupPatchIDs();
         forAllConstIters(groupLookup, iter)
@@ -787,7 +787,7 @@ Foam::labelList Foam::polyBoundaryMesh::indices
     // Only check groups if requested and they exist
     if (useGroups && this->hasGroupIDs())
     {
-        ids.resize(2*this->size());
+        ids.reserve(this->size());
 
         const auto& groupLookup = groupPatchIDs();
         forAllConstIters(groupLookup, iter)
@@ -958,7 +958,7 @@ Foam::labelHashSet Foam::polyBoundaryMesh::patchSet
 
     const label len = patches.size();
 
-    ids.resize(2*len);
+    ids.reserve(len);
 
     // Only check groups if requested and they exist
     const bool checkGroups = (useGroups && this->hasGroupIDs());
diff --git a/src/OpenFOAM/meshes/polyMesh/polyMeshCheck/polyMeshCheck.C b/src/OpenFOAM/meshes/polyMesh/polyMeshCheck/polyMeshCheck.C
index 255335aafa..da62393871 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyMeshCheck/polyMeshCheck.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyMeshCheck/polyMeshCheck.C
@@ -373,11 +373,11 @@ bool Foam::polyMesh::checkEdgeAlignment
 
         if (setPtr)
         {
-            setPtr->resize(2*edgesInError.size());
+            setPtr->reserve(2*edgesInError.size());
             forAllConstIters(edgesInError, iter)
             {
-                setPtr->insert(iter.key()[0]);
-                setPtr->insert(iter.key()[1]);
+                setPtr->insert(iter.key().first());
+                setPtr->insert(iter.key().second());
             }
         }
 
diff --git a/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C b/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
index 7afd9d8969..dbd296f421 100644
--- a/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
+++ b/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
@@ -104,7 +104,7 @@ void Foam::syncTools::syncPointMap
         // global shared index per local index
         const labelList& sharedPtAddr = pd.sharedPointAddr();
 
-        sharedPointValues.resize(sharedPtAddr.size());
+        sharedPointValues.reserve(sharedPtAddr.size());
 
         // Fill my entries in the shared points
         forAll(sharedPtLabels, i)
diff --git a/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C b/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C
index 63e3747836..ed35f4a341 100644
--- a/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C
+++ b/src/OpenFOAM/meshes/polyMesh/zones/ZoneMesh/ZoneMesh.C
@@ -384,7 +384,7 @@ Foam::labelList Foam::ZoneMesh<ZoneType, MeshType>::indices
 
     if (checkGroups)
     {
-        ids.resize(2*this->size());
+        ids.reserve(this->size());
     }
 
     if (matcher.isPattern())
@@ -459,7 +459,7 @@ Foam::labelList Foam::ZoneMesh<ZoneType, MeshType>::indices
     // Only check groups if requested and they exist
     if (useGroups && this->hasGroupIDs())
     {
-        ids.resize(2*this->size());
+        ids.reserve(this->size());
 
         const auto& groupLookup = groupZoneIDs();
         forAllConstIters(groupLookup, iter)
@@ -505,7 +505,7 @@ Foam::labelList Foam::ZoneMesh<ZoneType, MeshType>::indices
     // Only check groups if requested and they exist
     if (useGroups && this->hasGroupIDs())
     {
-        ids.resize(2*this->size());
+        ids.reserve(this->size());
 
         const auto& groupLookup = groupZoneIDs();
         forAllConstIters(groupLookup, iter)
diff --git a/src/OpenFOAM/meshes/primitiveMesh/PrimitivePatch/PrimitivePatchBdryPoints.C b/src/OpenFOAM/meshes/primitiveMesh/PrimitivePatch/PrimitivePatchBdryPoints.C
index 17190d0a1e..b5fdf6d8d1 100644
--- a/src/OpenFOAM/meshes/primitiveMesh/PrimitivePatch/PrimitivePatchBdryPoints.C
+++ b/src/OpenFOAM/meshes/primitiveMesh/PrimitivePatch/PrimitivePatchBdryPoints.C
@@ -51,7 +51,7 @@ Foam::PrimitivePatch<FaceList, PointField>::calcBdryPoints() const
             << "Calculating boundary points from existing addressing"
             << nl;
 
-        bp.resize(4*nBoundaryEdges());
+        bp.reserve(2*nBoundaryEdges());
 
         for (const edge& e : boundaryEdges())
         {
@@ -103,7 +103,7 @@ Foam::PrimitivePatch<FaceList, PointField>::calcBdryPoints() const
             }
         }
 
-        bp.resize(4*edgeCount);
+        bp.reserve(2*edgeCount);
 
         forAllConstIters(knownEdges, iter)
         {
diff --git a/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCheck/primitiveMeshCheck.C b/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCheck/primitiveMeshCheck.C
index c45ad6ca4b..24b36c89e7 100644
--- a/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCheck/primitiveMeshCheck.C
+++ b/src/OpenFOAM/meshes/primitiveMesh/primitiveMeshCheck/primitiveMeshCheck.C
@@ -1512,7 +1512,7 @@ bool Foam::primitiveMesh::checkFaceFaces
     label nBaffleFaces = 0;
     label nErrorDuplicate = 0;
     label nErrorOrder = 0;
-    Map<label> nCommonPoints(128);
+    Map<label> nCommonPoints;
 
     for (label facei = 0; facei < nFaces(); facei++)
     {
diff --git a/src/OpenFOAM/parallel/processorTopology/processorTopologyNew.H b/src/OpenFOAM/parallel/processorTopology/processorTopologyNew.H
index 17384f3532..aa25fea0f8 100644
--- a/src/OpenFOAM/parallel/processorTopology/processorTopologyNew.H
+++ b/src/OpenFOAM/parallel/processorTopology/processorTopologyNew.H
@@ -95,7 +95,7 @@ Foam::processorTopology Foam::processorTopology::New
         // - assumes single connections between processors
 
         auto& patchMap = topo.procPatchMap_;
-        patchMap.resize(2*numProcPatches);
+        patchMap.reserve(numProcPatches);
 
         forAll(patches, patchi)
         {
diff --git a/src/OpenFOAM/primitives/strings/lists/hashedWordList.C b/src/OpenFOAM/primitives/strings/lists/hashedWordList.C
index f8737e5857..bd5e9217bb 100644
--- a/src/OpenFOAM/primitives/strings/lists/hashedWordList.C
+++ b/src/OpenFOAM/primitives/strings/lists/hashedWordList.C
@@ -35,7 +35,7 @@ void Foam::hashedWordList::rehash() const
     const label len = list.size();
 
     lookup_.clear();
-    lookup_.resize(2*len);
+    lookup_.reserve(len);
 
     for (label i = 0; i < len; ++i)
     {
@@ -50,7 +50,7 @@ void Foam::hashedWordList::uniq()
     const label len = list.size();
 
     lookup_.clear();
-    lookup_.resize(2*len);
+    lookup_.reserve(len);
 
     label count = 0;
 
diff --git a/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C b/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C
index b32abd951f..ff8f00d5e5 100644
--- a/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C
+++ b/src/dynamicFvMesh/dynamicRefineFvMesh/dynamicRefineFvMesh.C
@@ -184,7 +184,7 @@ void Foam::dynamicRefineFvMesh::readDict()
     auto fluxVelocities = refineDict.get<List<Pair<word>>>("correctFluxes");
 
     // Rework into hashtable.
-    correctFluxes_.resize(fluxVelocities.size());
+    correctFluxes_.reserve(fluxVelocities.size());
     for (const auto& pr : fluxVelocities)
     {
         correctFluxes_.insert(pr.first(), pr.second());
diff --git a/src/dynamicMesh/meshCut/meshModifiers/boundaryCutter/boundaryCutter.C b/src/dynamicMesh/meshCut/meshModifiers/boundaryCutter/boundaryCutter.C
index 8d27e71951..a58517cec3 100644
--- a/src/dynamicMesh/meshCut/meshModifiers/boundaryCutter/boundaryCutter.C
+++ b/src/dynamicMesh/meshCut/meshModifiers/boundaryCutter/boundaryCutter.C
@@ -408,7 +408,7 @@ void Foam::boundaryCutter::setRefinement
     edgeAddedPoints_.clear();
 
     faceAddedPoint_.clear();
-    faceAddedPoint_.resize(faceToFeaturePoint.size());
+    faceAddedPoint_.reserve(faceToFeaturePoint.size());
 
 
     //
@@ -813,7 +813,7 @@ void Foam::boundaryCutter::setRefinement
 
     // Convert edge to points storage from edge labels (not preserved)
     // to point labels
-    edgeAddedPoints_.resize(edgeToCuts.size());
+    edgeAddedPoints_.reserve(edgeToAddedPoints.size());
 
     forAllConstIters(edgeToAddedPoints, iter)
     {
@@ -832,7 +832,7 @@ void Foam::boundaryCutter::updateMesh(const mapPolyMesh& morphMap)
 
     {
         // Create copy since we're deleting entries.
-        Map<label> newAddedPoints(faceAddedPoint_.size());
+        Map<label> newAddedPoints(faceAddedPoint_.capacity());
 
         forAllConstIters(faceAddedPoint_, iter)
         {
@@ -860,7 +860,7 @@ void Foam::boundaryCutter::updateMesh(const mapPolyMesh& morphMap)
 
     {
         // Create copy since we're deleting entries
-        EdgeMap<labelList> newEdgeAddedPoints(edgeAddedPoints_.size());
+        EdgeMap<labelList> newEdgeAddedPoints(edgeAddedPoints_.capacity());
 
         forAllConstIters(edgeAddedPoints_, iter)
         {
diff --git a/src/dynamicMesh/meshCut/meshModifiers/meshCutAndRemove/meshCutAndRemove.C b/src/dynamicMesh/meshCut/meshModifiers/meshCutAndRemove/meshCutAndRemove.C
index 239ec27dbd..0468de2e5c 100644
--- a/src/dynamicMesh/meshCut/meshModifiers/meshCutAndRemove/meshCutAndRemove.C
+++ b/src/dynamicMesh/meshCut/meshModifiers/meshCutAndRemove/meshCutAndRemove.C
@@ -583,10 +583,10 @@ void Foam::meshCutAndRemove::setRefinement
 {
     // Clear and size maps here since mesh size will change.
     addedFaces_.clear();
-    addedFaces_.resize(cuts.nLoops());
+    addedFaces_.reserve(cuts.nLoops());
 
     addedPoints_.clear();
-    addedPoints_.resize(cuts.nLoops());
+    addedPoints_.reserve(cuts.nLoops());
 
     if (cuts.nLoops() == 0)
     {
diff --git a/src/dynamicMesh/meshCut/meshModifiers/meshCutter/meshCutter.C b/src/dynamicMesh/meshCut/meshModifiers/meshCutter/meshCutter.C
index d79b6c5918..37a800ab39 100644
--- a/src/dynamicMesh/meshCut/meshModifiers/meshCutter/meshCutter.C
+++ b/src/dynamicMesh/meshCut/meshModifiers/meshCutter/meshCutter.C
@@ -526,13 +526,13 @@ void Foam::meshCutter::setRefinement
 {
     // Clear and size maps here since mesh size will change.
     addedCells_.clear();
-    addedCells_.resize(cuts.nLoops());
+    addedCells_.reserve(cuts.nLoops());
 
     addedFaces_.clear();
-    addedFaces_.resize(cuts.nLoops());
+    addedFaces_.reserve(cuts.nLoops());
 
     addedPoints_.clear();
-    addedPoints_.resize(cuts.nLoops());
+    addedPoints_.reserve(cuts.nLoops());
 
     if (!returnReduceOr(cuts.nLoops()))
     {
diff --git a/src/dynamicMesh/polyMeshAdder/faceCoupleInfo.C b/src/dynamicMesh/polyMeshAdder/faceCoupleInfo.C
index 7b4bc566a7..bbe666c31f 100644
--- a/src/dynamicMesh/polyMeshAdder/faceCoupleInfo.C
+++ b/src/dynamicMesh/polyMeshAdder/faceCoupleInfo.C
@@ -514,7 +514,7 @@ void Foam::faceCoupleInfo::setCutEdgeToPoints(const labelList& cutToMasterEdges)
     const edgeList& cutEdges = cutFaces().edges();
 
     // Size extra big so searching is faster
-    cutEdgeToPoints_.resize
+    cutEdgeToPoints_.reserve
     (
         masterPatch().nEdges()
       + slavePatch().nEdges()
@@ -1254,7 +1254,7 @@ Foam::label Foam::faceCoupleInfo::matchEdgeFaces
 
     // For every unassigned cutFacei the possible list of master faces.
     candidates.clear();
-    candidates.resize(cutFaces().size());
+    candidates.reserve(cutFaces().size());
 
     label nChanged = 0;
 
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/addPatchCellLayer.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/addPatchCellLayer.C
index f0441afd67..c369d7246e 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/addPatchCellLayer.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/addPatchCellLayer.C
@@ -1884,7 +1884,7 @@ void Foam::addPatchCellLayer::setRefinement
     // For now just keep it connected to the original.
     {
         // Work space
-        Map<label> minPointValue(128);
+        Map<label> minPointValue;
         faceList oldBoundaryFaces(mesh_.nBoundaryFaces());
 
         while (true)
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/edgeCollapser.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/edgeCollapser.C
index 2e1b557c42..46df773fe2 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/edgeCollapser.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/edgeCollapser.C
@@ -1316,7 +1316,7 @@ bool Foam::edgeCollapser::setRefinement
         }
 
         // 2. Size
-        collapseStrings.resize(2*nPerIndex.size());
+        collapseStrings.reserve(nPerIndex.size());
         forAllConstIters(nPerIndex, iter)
         {
             collapseStrings.insert(iter.key(), DynamicList<label>(iter.val()));
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
index ad16095498..ce5548367c 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
@@ -4163,7 +4163,7 @@ void Foam::hexRef8::storeData
 )
 {
     savedPointLevel_.clear();
-    savedPointLevel_.resize(2*pointsToStore.size());
+    savedPointLevel_.reserve(pointsToStore.size());
     forAll(pointsToStore, i)
     {
         label pointi = pointsToStore[i];
@@ -4171,7 +4171,7 @@ void Foam::hexRef8::storeData
     }
 
     savedCellLevel_.clear();
-    savedCellLevel_.resize(2*cellsToStore.size());
+    savedCellLevel_.reserve(cellsToStore.size());
     forAll(cellsToStore, i)
     {
         label celli = cellsToStore[i];
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/removePoints.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/removePoints.C
index c2d9bf584a..9dbed92810 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/removePoints.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/removePoints.C
@@ -319,8 +319,8 @@ void Foam::removePoints::setRefinement
     // Size undo storage
     if (undoable_)
     {
-        savedPoints_.setSize(nDeleted);
-        pointToSaved.resize(2*nDeleted);
+        savedPoints_.resize(nDeleted);
+        pointToSaved.reserve(nDeleted);
     }
 
 
diff --git a/src/finiteArea/faMesh/faBoundaryMesh/faBoundaryMesh.C b/src/finiteArea/faMesh/faBoundaryMesh/faBoundaryMesh.C
index 8717ef5af3..2417132a1e 100644
--- a/src/finiteArea/faMesh/faBoundaryMesh/faBoundaryMesh.C
+++ b/src/finiteArea/faMesh/faBoundaryMesh/faBoundaryMesh.C
@@ -490,7 +490,7 @@ Foam::labelList Foam::faBoundaryMesh::indices
     {
         if (checkGroups)
         {
-            ids.resize(2*this->size());
+            ids.reserve(this->size());
 
             const auto& groupLookup = groupPatchIDs();
             forAllConstIters(groupLookup, iter)
@@ -559,7 +559,7 @@ Foam::labelList Foam::faBoundaryMesh::indices
     // Only check groups if requested and they exist
     if (useGroups && this->hasGroupIDs())
     {
-        ids.resize(2*this->size());
+        ids.reserve(this->size());
 
         const auto& groupLookup = groupPatchIDs();
         forAllConstIters(groupLookup, iter)
@@ -604,7 +604,7 @@ Foam::labelList Foam::faBoundaryMesh::indices
     // Only check groups if requested and they exist
     if (useGroups && this->hasGroupIDs())
     {
-        ids.resize(2*this->size());
+        ids.reserve(this->size());
 
         const auto& groupLookup = groupPatchIDs();
         forAllConstIters(groupLookup, iter)
diff --git a/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CECCellToCellStencil.C b/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CECCellToCellStencil.C
index 496abb1ddb..4e6698efb7 100644
--- a/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CECCellToCellStencil.C
+++ b/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CECCellToCellStencil.C
@@ -39,7 +39,7 @@ void Foam::CECCellToCellStencil::calcEdgeBoundaryData
     EdgeMap<labelList>& neiGlobal
 ) const
 {
-    neiGlobal.resize(2*boundaryEdges.size());
+    neiGlobal.reserve(boundaryEdges.size());
 
     labelHashSet edgeGlobals;
 
diff --git a/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CPCCellToCellStencil.C b/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CPCCellToCellStencil.C
index d62d13c4fd..c39ac159b6 100644
--- a/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CPCCellToCellStencil.C
+++ b/src/finiteVolume/fvMesh/extendedStencil/cellToCell/globalIndexStencils/CPCCellToCellStencil.C
@@ -38,7 +38,7 @@ void Foam::CPCCellToCellStencil::calcPointBoundaryData
     Map<labelList>& neiGlobal
 ) const
 {
-    neiGlobal.resize(2*boundaryPoints.size());
+    neiGlobal.reserve(boundaryPoints.size());
 
     labelHashSet pointGlobals;
 
diff --git a/src/finiteVolume/fvMesh/extendedStencil/cellToFace/globalIndexStencils/FECCellToFaceStencil.C b/src/finiteVolume/fvMesh/extendedStencil/cellToFace/globalIndexStencils/FECCellToFaceStencil.C
index afc9845ac3..63ed3f7840 100644
--- a/src/finiteVolume/fvMesh/extendedStencil/cellToFace/globalIndexStencils/FECCellToFaceStencil.C
+++ b/src/finiteVolume/fvMesh/extendedStencil/cellToFace/globalIndexStencils/FECCellToFaceStencil.C
@@ -40,7 +40,7 @@ void Foam::FECCellToFaceStencil::calcEdgeBoundaryData
     EdgeMap<labelList>& neiGlobal
 ) const
 {
-    neiGlobal.resize(2*boundaryEdges.size());
+    neiGlobal.reserve(boundaryEdges.size());
 
     labelHashSet edgeGlobals;
 
diff --git a/src/finiteVolume/fvMesh/wallDist/wallDistAddressing/wallDistAddressing.C b/src/finiteVolume/fvMesh/wallDist/wallDistAddressing/wallDistAddressing.C
index c6639c2857..e7f21e66b2 100644
--- a/src/finiteVolume/fvMesh/wallDist/wallDistAddressing/wallDistAddressing.C
+++ b/src/finiteVolume/fvMesh/wallDist/wallDistAddressing/wallDistAddressing.C
@@ -222,7 +222,7 @@ void Foam::wallDistAddressing::correct(volScalarField& y)
     Map<label> cellToWallFace;
     if (correctWalls_)
     {
-        cellToWallFace.resize(2*nWalls);
+        cellToWallFace.reserve(nWalls);
         correctBoundaryFaceCells
         (
             patchSet,
diff --git a/src/finiteVolume/fvMesh/zoneDistribute/zoneStencils/zoneCPCStencil.C b/src/finiteVolume/fvMesh/zoneDistribute/zoneStencils/zoneCPCStencil.C
index c32751b733..8f6ae13f09 100644
--- a/src/finiteVolume/fvMesh/zoneDistribute/zoneStencils/zoneCPCStencil.C
+++ b/src/finiteVolume/fvMesh/zoneDistribute/zoneStencils/zoneCPCStencil.C
@@ -91,7 +91,7 @@ void Foam::zoneCPCStencil::calcPointBoundaryData
     Map<labelList>& neiGlobal
 ) const
 {
-    neiGlobal.resize(2*boundaryPoints.size());
+    neiGlobal.reserve(boundaryPoints.size());
 
     labelHashSet pointGlobals;
 
diff --git a/src/functionObjects/field/nearWallFields/nearWallFields.C b/src/functionObjects/field/nearWallFields/nearWallFields.C
index 5aeaf99c93..45c0a87c13 100644
--- a/src/functionObjects/field/nearWallFields/nearWallFields.C
+++ b/src/functionObjects/field/nearWallFields/nearWallFields.C
@@ -284,8 +284,8 @@ bool Foam::functionObjects::nearWallFields::read(const dictionary& dict)
     // Generate fields with mappedField boundary condition
 
     // Convert field to map
-    fieldMap_.resize(2*fieldSet_.size());
-    reverseFieldMap_.resize(2*fieldSet_.size());
+    fieldMap_.reserve(fieldSet_.size());
+    reverseFieldMap_.reserve(fieldSet_.size());
     forAll(fieldSet_, seti)
     {
         const word& fldName = fieldSet_[seti].first();
diff --git a/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C b/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C
index 83f7c096e8..aaf99f953e 100644
--- a/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C
+++ b/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C
@@ -147,7 +147,7 @@ void Foam::MGridGenGAMGAgglomeration::detectSharedFaces
     const labelUList& upper = addr.upperAddr();
 
     sharedFaces.clear();
-    sharedFaces.resize(addr.lowerAddr().size()/100);
+    sharedFaces.reserve(addr.lowerAddr().size()/100);
 
     // Detect any faces inbetween same value
     forAll(lower, facei)
diff --git a/src/fvAgglomerationMethods/pairPatchAgglomeration/pairPatchAgglomeration.C b/src/fvAgglomerationMethods/pairPatchAgglomeration/pairPatchAgglomeration.C
index 8bc9ed667e..16314968ad 100644
--- a/src/fvAgglomerationMethods/pairPatchAgglomeration/pairPatchAgglomeration.C
+++ b/src/fvAgglomerationMethods/pairPatchAgglomeration/pairPatchAgglomeration.C
@@ -175,7 +175,7 @@ void Foam::pairPatchAgglomeration::setEdgeWeights
 
     // Clean old weights
     facePairWeight_.clear();
-    facePairWeight_.resize(coarsePatch.nEdges());
+    facePairWeight_.reserve(coarsePatch.nEdges());
 
     for (label i = 0; i < coarsePatch.nInternalEdges(); i++)
     {
diff --git a/src/fvOptions/sources/general/semiImplicitSource/SemiImplicitSource.C b/src/fvOptions/sources/general/semiImplicitSource/SemiImplicitSource.C
index 1011eb1823..c8830ae3d7 100644
--- a/src/fvOptions/sources/general/semiImplicitSource/SemiImplicitSource.C
+++ b/src/fvOptions/sources/general/semiImplicitSource/SemiImplicitSource.C
@@ -63,18 +63,18 @@ void Foam::fv::SemiImplicitSource<Type>::setFieldCoeffs
 
     Su_.clear();
     Sp_.clear();
-    Su_.resize(2*count);
-    Sp_.resize(2*count);
+    Su_.reserve(count);
+    Sp_.reserve(count);
 
     driverSu_.clear();
     driverSp_.clear();
-    driverSu_.resize(2*count);
-    driverSp_.resize(2*count);
+    driverSu_.reserve(count);
+    driverSp_.reserve(count);
 
     valueExprSu_.clear();
     valueExprSp_.clear();
-    valueExprSu_.resize(2*count);
-    valueExprSp_.resize(2*count);
+    valueExprSu_.reserve(count);
+    valueExprSp_.reserve(count);
 
     fv::option::resetApplied();
 
diff --git a/src/meshTools/regionSplit/localPointRegion.C b/src/meshTools/regionSplit/localPointRegion.C
index 02d2e8aea3..c4dd9b2eef 100644
--- a/src/meshTools/regionSplit/localPointRegion.C
+++ b/src/meshTools/regionSplit/localPointRegion.C
@@ -684,7 +684,7 @@ Foam::List<Foam::labelPair> Foam::localPointRegion::findDuplicateFacePairs
 void Foam::localPointRegion::updateMesh(const mapPolyMesh& map)
 {
     {
-        Map<label> newMap(meshFaceMap_.size());
+        Map<label> newMap(2*meshFaceMap_.size());
 
         forAllConstIters(meshFaceMap_, iter)
         {
@@ -698,7 +698,7 @@ void Foam::localPointRegion::updateMesh(const mapPolyMesh& map)
         meshFaceMap_.transfer(newMap);
     }
     {
-        Map<label> newMap(meshPointMap_.size());
+        Map<label> newMap(2*meshPointMap_.size());
 
         forAllConstIters(meshPointMap_, iter)
         {
diff --git a/src/meshTools/regionSplit/regionSplit.C b/src/meshTools/regionSplit/regionSplit.C
index 20ca5ece34..9e02486ed5 100644
--- a/src/meshTools/regionSplit/regionSplit.C
+++ b/src/meshTools/regionSplit/regionSplit.C
@@ -721,17 +721,16 @@ Foam::regionSplit::reduceRegionsImpl
     labelListList sendNonLocal(Pstream::nProcs());
 
     {
-        List<labelHashSet> nonLocal(Pstream::nProcs(), labelHashSet(0));
+        List<labelHashSet> nonLocal(Pstream::nProcs());
 
         // Use estimate of sizing for non-local regions
+        label estimatedCount((nLocalRegions-nCompact)/Pstream::nProcs());
+
         forAll(nonLocal, proci)
         {
             if (proci != Pstream::myProcNo())
             {
-                nonLocal[proci].resize
-                (
-                    2*((nLocalRegions-nCompact)/Pstream::nProcs())
-                );
+                nonLocal[proci].reserve(estimatedCount);
             }
         }
 
diff --git a/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C b/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C
index 0cc6121635..a834769306 100644
--- a/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C
+++ b/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C
@@ -117,7 +117,7 @@ bool Foam::triSurfaceMesh::isSurfaceClosed() const
     // Every edge should be used by two faces exactly.
     // To prevent doing work twice per edge only look at edges to higher
     // point
-    EdgeMap<label> facesPerEdge(128);
+    EdgeMap<label> facesPerEdge;
     forAll(pointFaces, pointi)
     {
         const labelList& pFaces = pointFaces[pointi];
diff --git a/src/meshTools/topoSet/topoSets/cellSet.C b/src/meshTools/topoSet/topoSets/cellSet.C
index 4e2ca99bc3..7df945566e 100644
--- a/src/meshTools/topoSet/topoSets/cellSet.C
+++ b/src/meshTools/topoSet/topoSets/cellSet.C
@@ -220,7 +220,7 @@ void Foam::cellSet::distribute(const mapDistributePolyMesh& map)
     // Update labelHashSet
 
     labels.clear();
-    labels.resize(2*n);
+    labels.reserve(n);
 
     for (label i=0; i < len; ++i)
     {
diff --git a/src/meshTools/topoSet/topoSets/cellZoneSet.C b/src/meshTools/topoSet/topoSets/cellZoneSet.C
index 6e9876439a..28ab5ac500 100644
--- a/src/meshTools/topoSet/topoSets/cellZoneSet.C
+++ b/src/meshTools/topoSet/topoSets/cellZoneSet.C
@@ -50,7 +50,7 @@ void Foam::cellZoneSet::updateSet()
     inplaceReorder(order, addressing_);
 
     cellSet::clearStorage();
-    cellSet::resize(2*addressing_.size());
+    cellSet::reserve(addressing_.size());
     cellSet::set(addressing_);
 }
 
diff --git a/src/meshTools/topoSet/topoSets/faceSet.C b/src/meshTools/topoSet/topoSets/faceSet.C
index 053ee10527..1a87e4f9b7 100644
--- a/src/meshTools/topoSet/topoSets/faceSet.C
+++ b/src/meshTools/topoSet/topoSets/faceSet.C
@@ -199,7 +199,7 @@ void Foam::faceSet::distribute(const mapDistributePolyMesh& map)
     // Update labelHashSet
 
     labels.clear();
-    labels.resize(2*n);
+    labels.reserve(n);
 
     for (label i=0; i < len; ++i)
     {
diff --git a/src/meshTools/topoSet/topoSets/faceZoneSet.C b/src/meshTools/topoSet/topoSets/faceZoneSet.C
index 5ea533e8f8..41177225c1 100644
--- a/src/meshTools/topoSet/topoSets/faceZoneSet.C
+++ b/src/meshTools/topoSet/topoSets/faceZoneSet.C
@@ -55,7 +55,7 @@ void Foam::faceZoneSet::updateSet()
     flipMap_ = boolUIndList(flipMap_, order)();
 
     faceSet::clearStorage();
-    faceSet::resize(2*addressing_.size());
+    faceSet::reserve(addressing_.size());
     faceSet::set(addressing_);
 }
 
diff --git a/src/meshTools/topoSet/topoSets/pointSet.C b/src/meshTools/topoSet/topoSets/pointSet.C
index 68e3b87e44..6c4bc3a862 100644
--- a/src/meshTools/topoSet/topoSets/pointSet.C
+++ b/src/meshTools/topoSet/topoSets/pointSet.C
@@ -201,7 +201,7 @@ void Foam::pointSet::distribute(const mapDistributePolyMesh& map)
     // Update labelHashSet
 
     labels.clear();
-    labels.resize(2*n);
+    labels.reserve(n);
 
     for (label i=0; i < len; ++i)
     {
diff --git a/src/meshTools/topoSet/topoSets/pointZoneSet.C b/src/meshTools/topoSet/topoSets/pointZoneSet.C
index c5392867e3..cd0e151d61 100644
--- a/src/meshTools/topoSet/topoSets/pointZoneSet.C
+++ b/src/meshTools/topoSet/topoSets/pointZoneSet.C
@@ -51,7 +51,7 @@ void Foam::pointZoneSet::updateSet()
     inplaceReorder(order, addressing_);
 
     pointSet::clearStorage();
-    pointSet::resize(2*addressing_.size());
+    pointSet::reserve(addressing_.size());
     pointSet::set(addressing_);
 }
 
diff --git a/src/meshTools/topoSet/topoSets/topoSet.C b/src/meshTools/topoSet/topoSets/topoSet.C
index 31e47c8981..f83680e0e8 100644
--- a/src/meshTools/topoSet/topoSets/topoSet.C
+++ b/src/meshTools/topoSet/topoSets/topoSet.C
@@ -534,7 +534,7 @@ void Foam::topoSet::invert(const label maxLen)
     );
 
     clear();  // Maybe don't trust the previous move operation
-    resize(2*max(64, (maxLen - original.size())));
+    reserve(max(64, (maxLen - original.size())));
 
     for (label id=0; id < maxLen; ++id)
     {
diff --git a/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C b/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
index 17b92e868d..a0fa676559 100644
--- a/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
+++ b/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
@@ -801,7 +801,7 @@ void Foam::cellCellStencils::inverseDistance::markDonors
 //    {
 //        if (proci != Pstream::myProcNo())
 //        {
-//            nonLocal[proci].resize(2*nOriginating[proci]);
+//            nonLocal[proci].reserve(nOriginating[proci]);
 //        }
 //    }
 //
diff --git a/src/parallel/decompose/faDecompose/faMeshDecomposition.C b/src/parallel/decompose/faDecompose/faMeshDecomposition.C
index 49518eb545..a3775f461b 100644
--- a/src/parallel/decompose/faDecompose/faMeshDecomposition.C
+++ b/src/parallel/decompose/faDecompose/faMeshDecomposition.C
@@ -275,7 +275,7 @@ void Foam::faMeshDecomposition::decomposeMesh()
             ioAddr.rename("faceProcAddressing");
             labelIOList fvFaceProcAddressing(ioAddr);
 
-            fvFaceProcAddressingHash.resize(2*fvFaceProcAddressing.size());
+            fvFaceProcAddressingHash.reserve(fvFaceProcAddressing.size());
 
             forAll(fvFaceProcAddressing, facei)
             {
@@ -355,7 +355,7 @@ void Foam::faMeshDecomposition::decomposeMesh()
 
         Map<label>& curMap = procMeshEdgesMap_[procI];
         curMap.clear();
-        curMap.resize(2*procEdges.size());
+        curMap.reserve(procEdges.size());
 
         forAll(procEdges, edgeI)
         {
diff --git a/src/sampling/surface/cutting/cuttingSurfaceBaseTemplates.C b/src/sampling/surface/cutting/cuttingSurfaceBaseTemplates.C
index 9438c64eed..ad3bca9c5a 100644
--- a/src/sampling/surface/cutting/cuttingSurfaceBaseTemplates.C
+++ b/src/sampling/surface/cutting/cuttingSurfaceBaseTemplates.C
@@ -67,10 +67,10 @@ void Foam::cuttingSurfaceBase::walkCellCuts
     DynamicList<label> localFaceLoop(16);
 
     // Local scratch space for edge to pointId
-    EdgeMap<label> localEdges(128);
+    EdgeMap<label> localEdges;
 
     // Local scratch space for edge to faceId
-    EdgeMap<edge>  localFaces(128);
+    EdgeMap<edge>  localFaces;
 
     // Avoid duplicates for cuts exactly through a mesh point.
     // No other way to distinguish them, since there is no single edge
diff --git a/src/sampling/surface/isoSurface/isoSurfaceTopo.C b/src/sampling/surface/isoSurface/isoSurfaceTopo.C
index 9e04a21863..8bade733be 100644
--- a/src/sampling/surface/isoSurface/isoSurfaceTopo.C
+++ b/src/sampling/surface/isoSurface/isoSurfaceTopo.C
@@ -206,7 +206,7 @@ Foam::isoSurfaceTopo::tetCutAddressing::tetCutAddressing
     if (useSnap)
     {
         // Some, but not all, cells may have point snapping
-        snapVertsLookup_.resize(4*nCutCells);
+        snapVertsLookup_.reserve(2*nCutCells);
     }
     if (debugCutTetsOn_)
     {
@@ -1390,7 +1390,7 @@ Foam::isoSurfaceTopo::isoSurfaceTopo
             const labelList& mp = s.meshPoints();
             const edgeList& surfEdges = s.edges();
             const labelListList& edgeFaces = s.edgeFaces();
-            openEdgeIds.resize(2*s.size());
+            openEdgeIds.reserve(s.size());
 
             forAll(edgeFaces, edgei)
             {