From 323daeda3c0be16477b68fd506ba785574599981 Mon Sep 17 00:00:00 2001
From: Mark Olesen <Mark.Olesen@esi-group.com>
Date: Thu, 3 Mar 2022 18:35:11 +0100
Subject: [PATCH] ENH: update CompactListList code

- eliminate redundant size_ accounting

- drop extra 'Container' template parameter and replace functionality
  with more flexible pack/unpack methods.
  There is also a pack() method that handles indirect lists of lists
  that can be used, for example, to pack a patch slice of faces.

  Drop the 'operator()' method in favour of unpack to expose and properly
  document the conversion. Should revisit the corresponding code in
  some places for optimization potential.

- align some method names with globalIndex:
  totalSize(), maxSize() etc
---
 .../CompactListList/Test-CompactListList.C    |  54 +-
 .../CompactListList/CompactListList.C         | 466 ++++++++-----
 .../CompactListList/CompactListList.H         | 435 +++++++++----
 .../CompactListList/CompactListListI.H        | 611 ++++++++++++------
 .../CompactListList/CompactListListIO.C       |  39 +-
 .../parallel/globalIndex/globalIndex.C        |  25 +-
 .../parallel/globalIndex/globalIndex.H        |   4 +-
 .../globalIndex/globalIndexTemplates.C        |  18 +-
 .../fvMeshDistribute/fvMeshDistribute.C       |   8 +-
 src/meshTools/polyTopoChange/polyTopoChange.C |   7 +-
 src/meshTools/polyTopoChange/polyTopoChange.H |   4 +-
 .../decompose/decompositionInformation.C      |   2 +-
 .../decompose/decompositionInformation.H      |   6 +-
 .../decompositionMethod/decompositionMethod.C |   2 +-
 .../metisLikeDecomp/metisLikeDecomp.C         |  27 +-
 .../multiLevelDecomp/multiLevelDecomp.C       |   4 +-
 .../decompose/ptscotchDecomp/ptscotchDecomp.C |  10 +-
 .../CuthillMcKeeRenumber.C                    |   4 +-
 .../renumberMethod/renumberMethod.C           |   6 +-
 .../renumberMethod/renumberMethod.H           |   8 +-
 .../springRenumber/springRenumber.C           |   4 +-
 21 files changed, 1170 insertions(+), 574 deletions(-)

diff --git a/applications/test/CompactListList/Test-CompactListList.C b/applications/test/CompactListList/Test-CompactListList.C
index 2b9593aa29..a8ad0d471e 100644
--- a/applications/test/CompactListList/Test-CompactListList.C
+++ b/applications/test/CompactListList/Test-CompactListList.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
+    Copyright (C) 2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -24,7 +25,7 @@ License
     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
 Application
-    CompactListListTest
+    Test-CompactListList
 
 Description
     Simple demonstration and test application for the CompactListList class.
@@ -32,6 +33,7 @@ Description
 \*---------------------------------------------------------------------------*/
 
 #include "CompactListList.H"
+#include "IndirectList.H"
 #include "IOstreams.H"
 #include "StringStream.H"
 #include "faceList.H"
@@ -44,9 +46,9 @@ using namespace Foam;
 int main(int argc, char *argv[])
 {
     {
-        // null construct
+        // Default construct
         CompactListList<label> cll1;
-        Info<< "cll1:" << cll1 << endl;
+        Info<< "cll1:" << cll1 << nl;
 
         // Resize and assign row by row
         labelList row0(2, Zero);
@@ -61,10 +63,12 @@ int main(int argc, char *argv[])
         cll1[1].deepCopy(row1);
         Info<< "cll1:" << cll1 << endl;
 
-        forAll(cll1.m(), i)
+        forAll(cll1.values(), i)
         {
             Info<< "i:" << i << " whichRow:" << cll1.whichRow(i) << endl;
         }
+
+        Info<< "unpack:" << cll1.unpack<face>() << endl;
     }
 
     List<List<label>> lll(5);
@@ -74,23 +78,23 @@ int main(int argc, char *argv[])
     lll[3].setSize(0, 3);
     lll[4].setSize(1, 4);
 
-    CompactListList<label> cll2(lll);
+    Info<< "packed:" << CompactListList<label>::pack(lll) << endl;
+
+    auto cll2(CompactListList<label>::pack(lll));
 
     Info<< "cll2  = " << cll2 << endl;
 
     forAll(cll2, i)
     {
-        Info<< cll2[i] << endl;
+        Info<< cll2[i] << nl;
     }
-
     Info<< endl;
 
     Info<< "cll2(2, 3) = " << cll2(2, 3) << nl << endl;
     cll2(2, 3) = 999;
     Info<< "cll2(2, 3) = " << cll2(2, 3) << nl << endl;
 
-    Info<< "cll2 as List<List<label >> " << cll2()
-        << endl;
+    Info<< "cll2 as List<List<label>> " << cll2.unpack() << endl;
 
     cll2.setSize(3);
 
@@ -140,16 +144,34 @@ int main(int argc, char *argv[])
         Info<< "cll5 = " << cll5 << endl;
     }
 
+    // Make some faces
     {
-        faceList fcs(2);
-        fcs[0] = face(labelList(1, label(111)));
-        fcs[1] = face(labelList(2, label(222)));
+        faceList fcs(5);
+        forAll(fcs, facei)
+        {
+            fcs[facei] = face(identity(4, facei));
+        }
 
-        CompactListList<label, face> compactFcs(fcs);
-        Info<< "comactFcs:" << compactFcs << endl;
+        Info<< "input faces: " << fcs << endl;
 
-        faceList fcs2 = compactFcs();
-        Info<< "fcs2:" << fcs2 << endl;
+        // From <face>
+        auto compactFcs(CompactListList<label>::pack<face>(fcs));
+        Info<< "compact faces:" << compactFcs << endl;
+
+        faceList fcs2 = compactFcs.unpack<face>();
+        Info<< "deserialized:" << fcs2 << endl;
+
+        // From some faces
+        IndirectList<face> subfaces(fcs, labelList({2, 4, 1}));
+
+        Info<< "sub faces: " << subfaces << endl;
+
+        auto subCompact
+        (
+            CompactListList<label>::pack(subfaces)
+        );
+        Info<< "compact faces:" << subCompact << endl;
+        Info<< "deserialized:" << subCompact.unpack() << endl;
     }
 
     return 0;
diff --git a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C
index ca1b88304a..4a0df991db 100644
--- a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C
+++ b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2021 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -27,181 +27,332 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "CompactListList.H"
+#include "labelRange.H"
+
+// * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
+
+template<class T>
+void Foam::CompactListList<T>::reportOverflowAndExit
+(
+    const label idx,
+    const labelUList& localLens
+)
+{
+    FatalErrorInFunction
+        << "Overflow : sum of sizes exceeds labelMax ("
+        << labelMax << ") after index " << idx;
+
+    if (!localLens.empty())
+    {
+        FatalError << " of " << flatOutput(localLens);
+    }
+
+    FatalError
+        << nl
+        << "Please recompile with larger datatype for label." << nl
+        << exit(FatalError);
+}
+
+
+template<class T>
+template<class ListListType>
+Foam::CompactListList<T> Foam::CompactListList<T>::packImpl
+(
+    const ListListType& lists,
+    const bool checkOverflow
+)
+{
+    CompactListList<T> compact;
+
+    auto& newOffsets = compact.offsets_;
+    auto& newValues = compact.values_;
+
+    label total = 0;
+    const label len = lists.size();
+
+    if (len)
+    {
+        newOffsets.resize(len+1, Zero);
+
+        for (label i = 0; i < len; ++i)
+        {
+            newOffsets[i] = total;
+            total += lists[i].size();
+
+            if (checkOverflow && total < newOffsets[i])
+            {
+                reportOverflowAndExit(i);
+            }
+        }
+        newOffsets[len] = total;
+    }
+
+    if (total)
+    {
+        // Copy in the data
+        newValues.resize(total);
+
+        auto outIter = newValues.begin();
+
+        for (const auto& list : lists)
+        {
+            forAll(list, i)
+            {
+                *outIter = list[i];
+                ++outIter;
+            }
+        }
+    }
+
+    return compact;
+}
+
+
+template<class T>
+template<class SubListType>
+Foam::CompactListList<T> Foam::CompactListList<T>::pack
+(
+    const UList<SubListType>& lists,
+    const bool checkOverflow
+)
+{
+    return CompactListList<T>::packImpl<UList<SubListType>>
+    (
+        lists,
+        checkOverflow
+    );
+}
+
+
+template<class T>
+template<class SubListType, class Addr>
+Foam::CompactListList<T> Foam::CompactListList<T>::pack
+(
+    const IndirectListBase<SubListType, Addr>& lists,
+    const bool checkOverflow
+)
+{
+    return CompactListList<T>::packImpl<IndirectListBase<SubListType, Addr>>
+    (
+        lists,
+        checkOverflow
+    );
+}
+
 
 // * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * * //
 
-template<class T, class Container>
-Foam::CompactListList<T, Container>::CompactListList(const List<Container>& ll)
-:
-    size_(ll.size()),
-    offsets_(ll.size()+1)
+template<class T>
+Foam::CompactListList<T>::CompactListList(const labelUList& listSizes)
 {
-    label sumSize = 0;
-    offsets_[0] = 0;
-    forAll(ll, i)
+    const label len = listSizes.size();
+
+    if (len)
     {
-        sumSize += ll[i].size();
-        offsets_[i+1] = sumSize;
-    }
+        offsets_.resize(len+1);
 
-    m_.setSize(sumSize);
-
-    label k = 0;
-    forAll(ll, i)
-    {
-        const Container& lli = ll[i];
-
-        forAll(lli, j)
+        label total = 0;
+        for (label i = 0; i < len; ++i)
         {
-            m_[k++] = lli[j];
+            offsets_[i] = total;
+            total += listSizes[i];
+
+#ifdef FULLDEBUG
+            if (total < offsets_[i])
+            {
+                reportOverflowAndExit(i, listSizes);
+            }
+#endif
         }
+
+        offsets_[len] = total;
+        values_.resize(total);
     }
 }
 
 
-template<class T, class Container>
-Foam::CompactListList<T, Container>::CompactListList
+template<class T>
+Foam::CompactListList<T>::CompactListList
 (
-    const labelUList& rowSizes
-)
-:
-    size_(rowSizes.size()),
-    offsets_(rowSizes.size()+1)
-{
-    label sumSize = 0;
-    offsets_[0] = 0;
-    forAll(rowSizes, i)
-    {
-        sumSize += rowSizes[i];
-        offsets_[i+1] = sumSize;
-    }
-
-    m_.setSize(sumSize);
-}
-
-
-template<class T, class Container>
-Foam::CompactListList<T, Container>::CompactListList
-(
-    const labelUList& rowSizes,
+    const labelUList& listSizes,
     const T& val
 )
-:
-    size_(rowSizes.size()),
-    offsets_(rowSizes.size()+1)
 {
-    label sumSize = 0;
-    offsets_[0] = 0;
-    forAll(rowSizes, i)
-    {
-        sumSize += rowSizes[i];
-        offsets_[i+1] = sumSize;
-    }
+    const label len = listSizes.size();
 
-    m_.setSize(sumSize, val);
+    if (len)
+    {
+        offsets_.resize(len+1);
+
+        label total = 0;
+        for (label i = 0; i < len; ++i)
+        {
+            offsets_[i] = total;
+            total += listSizes[i];
+
+#ifdef FULLDEBUG
+            if (total < offsets_[i])
+            {
+                reportOverflowAndExit(i, listSizes);
+            }
+#endif
+        }
+
+        offsets_[len] = total;
+        values_.resize(total, val);
+    }
 }
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-template<class T, class Container>
-void Foam::CompactListList<T, Container>::setSize(const label mRows)
+template<class T>
+Foam::label Foam::CompactListList<T>::maxNonLocalSize(const label rowi) const
 {
-    if (mRows == 0)
+    const label len = (offsets_.size() - 1);
+
+    if (len < 1)
+    {
+        return 0;
+    }
+
+    label maxLen = 0;
+
+    for (label i=0; i < len; ++i)
+    {
+        if (i != rowi)
+        {
+            const label localLen = (offsets_[i+1] - offsets_[i]);
+            maxLen = max(maxLen, localLen);
+        }
+    }
+
+    return maxLen;
+}
+
+
+template<class T>
+std::streamsize Foam::CompactListList<T>::byteSize() const
+{
+    if (!is_contiguous<T>::value)
+    {
+        FatalErrorInFunction
+            << "Invalid for non-contiguous data types"
+            << abort(FatalError);
+    }
+    return this->size_bytes();
+}
+
+
+template<class T>
+Foam::labelRange Foam::CompactListList<T>::range(const label i) const
+{
+    return labelRange(offsets_[i], offsets_[i+1] - offsets_[i]);
+}
+
+
+template<class T>
+Foam::List<Foam::labelRange>
+Foam::CompactListList<T>::ranges() const
+{
+    List<labelRange> values;
+
+    const label len = (offsets_.size() - 1);
+
+    if (len < 1)
+    {
+        return values;
+    }
+
+    values.resize(len);
+
+    for (label i=0; i < len; ++i)
+    {
+        values[i].reset(offsets_[i], (offsets_[i+1] - offsets_[i]));
+    }
+
+    return values;
+}
+
+
+template<class T>
+void Foam::CompactListList<T>::resize(const labelUList& listSizes)
+{
+    const label len = listSizes.size();
+
+    if (len)
+    {
+        offsets_.resize(len+1);
+
+        label total = 0;
+        for (label i = 0; i < len; ++i)
+        {
+            offsets_[i] = total;
+            total += listSizes[i];
+#if 0
+            if (checkOverflow && total < offsets_[i])
+            {
+                reportOverflowAndExit(i, listSizes);
+            }
+#endif
+        }
+
+        offsets_[len] = total;
+        values_.resize(total);
+    }
+    else
     {
         clear();
     }
-    if (mRows < size())
-    {
-        size_ = mRows;
-        offsets_.setSize(mRows+1);
-        m_.setSize(offsets_[mRows]);
-    }
-    else if (mRows > size())
-    {
-        FatalErrorInFunction
-            << "Cannot be used to extend the list from " << offsets_.size()
-            << " to " << mRows << nl
-            << "    Please use one of the other setSize member functions"
-            << abort(FatalError);
-    }
 }
 
 
-template<class T, class Container>
-void Foam::CompactListList<T, Container>::setSize
-(
-    const label mRows,
-    const label nData
-)
+template<class T>
+void Foam::CompactListList<T>::setLocalSize(const label rowi, const label len)
 {
-    size_ = mRows;
-    offsets_.setSize(mRows+1);
-    m_.setSize(nData);
-}
-
-
-template<class T, class Container>
-void Foam::CompactListList<T, Container>::setSize
-(
-    const label mRows,
-    const label nData,
-    const T& t
-)
-{
-    size_ = mRows;
-    offsets_.setSize(mRows+1);
-    m_.setSize(nData, t);
-}
-
-
-template<class T, class Container>
-void Foam::CompactListList<T, Container>::setSize(const labelUList& rowSizes)
-{
-    size_ = rowSizes.size();
-    offsets_.setSize(rowSizes.size()+1);
-
-    label sumSize = 0;
-    offsets_[0] = 0;
-    forAll(rowSizes, i)
+    if (rowi >= 0 && rowi+1 < offsets_.size() && len >= 0)
     {
-        sumSize += rowSizes[i];
-        offsets_[i+1] = sumSize;
-    }
+        const label delta = (len - (offsets_[rowi+1] - offsets_[rowi]));
 
-    m_.setSize(sumSize);
-}
-
-
-template<class T, class Container>
-Foam::labelList Foam::CompactListList<T, Container>::sizes() const
-{
-    labelList rowSizes(size());
-
-    if (rowSizes.size() > 0)
-    {
-        forAll(rowSizes, i)
+        // TBD: additional overflow check
+        if (delta)
         {
-            rowSizes[i] = offsets_[i+1] - offsets_[i];
+            for (label i = rowi+1; i < offsets_.size(); ++i)
+            {
+                offsets_[i] += delta;
+            }
         }
     }
-    return rowSizes;
 }
 
 
-template<class T, class Container>
-void Foam::CompactListList<T, Container>::clear()
+template<class T>
+Foam::labelList Foam::CompactListList<T>::localSizes() const
 {
-    size_ = 0;
-    offsets_.clear();
-    m_.clear();
+    labelList values;
+
+    const label len = (offsets_.size() - 1);
+
+    if (len < 1)
+    {
+        return values;
+    }
+
+    values.resize(len);
+
+    for (label i=0; i < len; ++i)
+    {
+        values[i] = offsets_[i+1] - offsets_[i];
+    }
+
+    return values;
 }
 
 
-template<class T, class Container>
-void Foam::CompactListList<T, Container>::swap
+template<class T>
+void Foam::CompactListList<T>::swap
 (
-    CompactListList<T, Container>& other
+    CompactListList<T>& other
 )
 {
     if (this == &other)
@@ -209,16 +360,15 @@ void Foam::CompactListList<T, Container>::swap
         return;  // Self-swap is a no-op
     }
 
-    std::swap(size_, other.size_);
     offsets_.swap(other.offsets_);
-    m_.swap(other.m_);
+    values_.swap(other.values_);
 }
 
 
-template<class T, class Container>
-void Foam::CompactListList<T, Container>::transfer
+template<class T>
+void Foam::CompactListList<T>::transfer
 (
-    CompactListList<T, Container>& list
+    CompactListList<T>& list
 )
 {
     if (this == &list)
@@ -226,25 +376,43 @@ void Foam::CompactListList<T, Container>::transfer
         return;  // Self-assignment is a no-op
     }
 
-    this->clear();
-    this->swap(list);
+    offsets_.transfer(list.offsets_);
+    values_.transfer(list.values_);
 }
 
 
-// * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
-
-template<class T, class Container>
-Foam::List<Container> Foam::CompactListList<T, Container>::operator()()
-const
+template<class T>
+template<class SubListType>
+Foam::List<SubListType>
+Foam::CompactListList<T>::unpack() const
 {
-    List<Container> ll(size());
+    List<SubListType> lists(size());
 
-    forAll(ll, i)
+    forAll(lists, i)
     {
-        ll[i] = Container(operator[](i));
+        lists[i] = SubListType(this->localList(i));
     }
 
-    return ll;
+    return lists;
+}
+
+
+template<class T>
+template<class SubListType>
+Foam::List<SubListType>
+Foam::CompactListList<T>::unpack(const labelRange& range) const
+{
+    List<SubListType> lists(range.size());
+
+    auto outIter = lists.begin();
+
+    for (const label i : range)
+    {
+        *outIter = SubListType(this->localList(i));
+        ++outIter;
+    }
+
+    return lists;
 }
 
 
diff --git a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H
index 9f62d65c2e..633fde0100 100644
--- a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H
+++ b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H
@@ -37,10 +37,8 @@ Description
       - offset[i] gives the index of first element of row i
       - offset[i+1] - offset[i] is the number of elements in row i
 
-    Storage is allocated on free-store during construction.
-
-    As a special case a null-constructed CompactListList has an empty
-    offsets_ (instead of size 1).
+    Note that an empty CompactListList should have empty offsets
+    (not size 1).
 
 SourceFiles
     CompactListList.C
@@ -49,10 +47,10 @@ SourceFiles
 
 \*---------------------------------------------------------------------------*/
 
-#ifndef CompactListList_H
-#define CompactListList_H
+#ifndef Foam_CompactListList_H
+#define Foam_CompactListList_H
 
-#include "labelList.H"
+#include "List.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -60,212 +58,399 @@ namespace Foam
 {
 
 // Forward Declarations
+template<class T> class CompactListList;
 
-template<class T, class Container> class CompactListList;
-
-template<class T, class Container> Istream& operator>>
-(
-    Istream&,
-    CompactListList<T, Container>&
-);
-template<class T, class Container> Ostream& operator<<
-(
-    Ostream&,
-    const CompactListList<T, Container>&
-);
+template<class T> Istream& operator>>(Istream&, CompactListList<T>&);
+template<class T> Ostream& operator<<(Ostream&, const CompactListList<T>&);
 
 
 /*---------------------------------------------------------------------------*\
                        Class CompactListList Declaration
 \*---------------------------------------------------------------------------*/
 
-template<class T, class Container = List<T>>
+template<class T>
 class CompactListList
 {
     // Private Data
 
-        label size_;
+        //- Offset (addressing) table
+        labelList offsets_;
 
-        //- Offset table
-        List<label> offsets_;
+        //- Packed (matrix) of values
+        List<T> values_;
 
-        //- Packed matrix of data
-        List<T> m_;
+
+    // Private Member Functions
+
+        //- Report overflow at specified index
+        static void reportOverflowAndExit
+        (
+            const label idx,
+            const labelUList& listSizes = labelUList::null()
+        );
+
+        //- Construct by packing together the list of lists
+        template<class ListListType>
+        static CompactListList<T> packImpl
+        (
+            const ListListType& lists,
+            const bool checkOverflow = false
+        );
+
+        //- Avoid poorly sized offsets/values
+        void enforceSizeSanity();
+
+        //- The max of localSizes, excluding the specified row
+        label maxNonLocalSize(const label rowi) const;
 
 
 public:
 
+    // STL type definitions
+
+        //- The value type the list contains
+        typedef T value_type;
+
+        //- The pointer type for non-const access to value_type items
+        typedef T* pointer;
+
+        //- The pointer type for const access to value_type items
+        typedef const T* const_pointer;
+
+        //- The type used for storing into value_type objects
+        typedef T& reference;
+
+        //- The type used for reading from constant value_type objects.
+        typedef const T& const_reference;
+
+        //- The type to represent the size of a CompactListList
+        typedef label size_type;
+
+
     // Static Member Functions
 
-        //- Return a null CompactListList
-        inline static const CompactListList<T, Container>& null();
+        //- Return a CompactListList reference to a nullObject
+        inline static const CompactListList<T>& null();
+
+        //- Construct by packing together the list of lists
+        template<class SubListType = List<T>>
+        static CompactListList<T> pack
+        (
+            const UList<SubListType>& lists,
+            const bool checkOverflow = false
+        );
+
+        //- Construct by packing together an indirect list of lists
+        template<class SubListType, class Addr>
+        static CompactListList<T> pack
+        (
+            const IndirectListBase<SubListType, Addr>& lists,
+            const bool checkOverflow = false
+        );
 
 
     // Constructors
 
         //- Default construct
-        inline CompactListList();
-
-        //- Construct by converting given List<List<T>>
-        explicit CompactListList(const List<Container>&);
-
-        //- Construct given size of offset table (number of rows)
-        //  and number of data.
-        inline CompactListList(const label mRows, const label nData);
-
-        //- Construct given size of offset table (number of rows),
-        //  the number of data and a value for all elements.
-        inline CompactListList(const label mRows, const label nData, const T&);
-
-        //- Construct given list of row-sizes.
-        explicit CompactListList(const labelUList& rowSizes);
-
-        //- Construct given list of row-sizes
-        CompactListList(const labelUList& rowSizes, const T&);
+        CompactListList() noexcept = default;
 
         //- Copy construct
-        inline CompactListList(const CompactListList<T, Container>& lst);
+        inline CompactListList(const CompactListList<T>& list);
 
         //- Move construct
-        inline CompactListList(CompactListList<T, Container>&& lst);
+        inline CompactListList(CompactListList<T>&& list);
 
-        //- Construct as copy or re-use as specified.
-        inline CompactListList(CompactListList<T, Container>& list, bool reuse);
+        //- Copy/move construct as specified.
+        inline CompactListList(CompactListList<T>& list, bool reuse);
+
+        //- Construct from number of rows and number of values.
+        inline CompactListList(const label mRows, const label nVals);
+
+        //- Construct from number of rows, number of values
+        //- initializing all elements to zero
+        inline CompactListList
+        (
+            const label mRows, const label nVals, const Foam::zero
+        );
+
+        //- Construct from number of rows, number of values
+        //- and uniform value for all elements.
+        inline CompactListList(const label mRows, const label nVals, const T&);
+
+        //- Construct given list of row-sizes.
+        explicit CompactListList(const labelUList& listSizes);
+
+        //- Construct given list of row-sizes and a uniform value
+        CompactListList(const labelUList& listSizes, const T& val);
 
         //- Construct from Istream.
-        CompactListList(Istream&);
+        explicit CompactListList(Istream& is);
 
         //- Clone
-        inline autoPtr<CompactListList<T, Container>> clone() const;
+        inline autoPtr<CompactListList<T>> clone() const;
 
 
     // Member Functions
 
-        // Access
+    // Access
 
-            //- True if the number of rows is zero
-            inline bool empty() const noexcept;
+        //- True if the number of rows/sublists is zero
+        inline bool empty() const noexcept;
 
-            //- The primary size (the number of rows)
-            inline label size() const noexcept;
+        //- The primary size (the number of rows/sublists)
+        inline label size() const noexcept;
 
-            //- The total addressed size
-            inline label totalSize() const;
+        //- The total addressed size
+        inline label totalSize() const;
 
-            //- Return the offset table (= size()+1)
-            inline const List<label>& offsets() const;
+        //- Return the offset table (= size()+1)
+        inline const labelList& offsets() const noexcept;
 
-            //- Return non-const access to the offset table
-            inline List<label>& offsets();
+        //- Return non-const access to the offset table
+        inline labelList& offsets() noexcept;
 
-            //- Return the packed matrix of data
-            inline const List<T>& m() const;
+        //- Return the packed matrix of values
+        inline const List<T>& values() const noexcept;
 
-            //- Return non-const access to the packed matrix of data
-            inline List<T>& m();
+        //- Return non-const access to the packed matrix of values
+        inline List<T>& values() noexcept;
 
 
-        // Edit
+        //- Return const pointer to the first data in values()
+        inline const T* cdata() const noexcept;
 
-            //- Reset size of CompactListList.
-            //  This form only allows contraction of the CompactListList.
-            void setSize(const label mRows);
+        //- Return pointer to the first data in values()
+        inline T* data() noexcept;
 
-            //- Reset size of CompactListList.
-            void setSize(const label mRows, const label nData);
+        //- Return const pointer to underlying values storage,
+        //- reinterpreted as byte data.
+        //  \note Only meaningful for contiguous data
+        inline const char* cdata_bytes() const noexcept;
 
-            //- Reset sizes of CompactListList and value for new elements.
-            void setSize(const label mRows, const label nData, const T&);
+        //- Return pointer to underlying values storage,
+        //- reinterpreted as byte data.
+        //  \note Only meaningful for contiguous data
+        inline char* data_bytes() noexcept;
 
-            //- Reset size of CompactListList.
-            void setSize(const labelUList& rowSizes);
+        //- Number of contiguous bytes for the values data,
+        //- no runtime check that the type is actually contiguous
+        //  \note Only meaningful for contiguous data
+        inline std::streamsize size_bytes() const noexcept;
 
-            //- Reset size of CompactListList.
-            //  This form only allows contraction of the CompactListList.
-            inline void resize(const label mRows);
-
-            //- Reset size of CompactListList.
-            inline void resize(const label mRows, const label nData);
-
-            //- Reset sizes of CompactListList and value for new elements.
-            inline void resize(const label mRows, const label nData, const T&);
-
-            //- Reset size of CompactListList.
-            inline void resize(const labelUList& rowSizes);
-
-            //- Clear the CompactListList, i.e. set sizes to zero.
-            void clear();
-
-            //- Return sizes (to be used e.g. for construction)
-            labelList sizes() const;
-
-            //- Swap contents
-            void swap(CompactListList<T, Container>& other);
-
-            //- Transfer contents into this and annul the argument
-            void transfer(CompactListList<T, Container>& list);
+        //- Number of contiguous bytes for the values data,
+        //- runtime FatalError if type is not contiguous
+        std::streamsize byteSize() const;
 
 
-        // Other
+    // Queries
 
-            //- Return index into m
-            inline label index(const label row, const label col) const;
+        //- The local row sizes. Same as localSizes
+        inline labelList sizes() const;
 
-            //- Get row for index into m.
-            inline label whichRow(const label index) const;
+        //- The local row starts
+        inline const labelUList localStarts() const;
 
-            //- Get column index (j) given above row
-            inline label whichColumn(const label row, const label index) const;
+        //- The local row sizes
+        labelList localSizes() const;
+
+        //- Starting offset for given row
+        inline label localStart(const label i) const;
+
+        //- End offset (exclusive) for given row
+        inline label localEnd(const label i) const;
+
+        //- Size of given row
+        inline label localSize(const label i) const;
+
+        //- Return start/size ranges for all sub-lists
+        List<labelRange> ranges() const;
+
+        //- Return start/size range for given sub-list
+        labelRange range(const label i) const;
+
+        //- The max row length used
+        inline label maxSize() const;
 
 
-    // Member Operators
+    // Edit
 
-        //- Return subscript-checked row as UList.
+        //- Clear addressing and contents
+        inline void clear();
+
+        //- Reset size of CompactListList.
+        //  \note this form only allows truncation of the CompactListList.
+        inline void resize(const label mRows);
+
+        //- Redimension CompactListList
+        inline void resize(const label mRows, const label nVals);
+
+        //- Redimension \em without preserving existing content
+        inline void resize_nocopy(const label mRows, const label nVals);
+
+        //- Redimension CompactListList and fill new elements with value.
+        inline void resize(const label mRows, const label nVals, const T&);
+
+        //- Reset dimensions of CompactListList
+        void resize(const labelUList& listSizes);
+
+        //- Alter local addressing size for given row, does not change content
+        void setLocalSize(const label rowi, const label len);
+
+
+        //- Redimension - same as resize()
+        inline void setSize(const label mRows);
+
+        //- Redimension - same as resize()
+        inline void setSize(const label mRows, const label nVals);
+
+        //- Redimension - same as resize()
+        inline void setSize(const label mRows, const label nVals, const T&);
+
+        //- Reset sizes - same as resize()
+        inline void setSize(const labelUList& listSizes);
+
+        //- Swap contents
+        void swap(CompactListList<T>& other);
+
+        //- Transfer contents into this and annul the argument
+        void transfer(CompactListList<T>& list);
+
+
+    // Global addressing queries
+
+        //- From local index on rowi to global (flat) indexing
+        //- into packed values
+        inline label toGlobal(const label rowi, const label i) const;
+
+        //- From global to local index on rowi
+        inline label toLocal(const label rowi, const label i) const;
+
+        //- Find row where global index comes from. Binary search.
+        //  \return -1 if out-of-bounds
+        inline label findRow(const label i) const;
+
+        //- Which row does global index come from? Binary search.
+        //  FatalError if out-of-bounds
+        inline label whichRow(const label i) const;
+
+
+    // Pack / Unpack
+
+        //- Return non-compact list of lists
+        template<class SubListType = List<T>>
+        List<SubListType> unpack() const;
+
+        //- Return non-compact list of lists for the range of sub-lists
+        template<class SubListType = List<T>>
+        List<SubListType> unpack(const labelRange& range) const;
+
+
+    // Assignment
+
+        //- Copy assignment
+        inline void operator=(const CompactListList<T>& list);
+
+        //- Move assignment
+        inline void operator=(CompactListList<T>&& list);
+
+        //- Assignment of all entries to the given value
+        inline void operator=(const T& val);
+
+        //- Assignment of all entries to zero
+        inline void operator=(const Foam::zero);
+
+
+    // Row-based access
+
+        //- Return non-const access to sub-list (no subscript checking)
+        inline UList<T> localList(const label i);
+
+        //- Return const access to sub-list (no subscript checking)
+        inline const UList<T> localList(const label i) const;
+
+        //- Return row as UList - same as localList method
         inline UList<T> operator[](const label i);
 
-        //- Return const subscript-checked row as UList.
+        //- Return row as const UList - same as localList method
         inline const UList<T> operator[](const label i) const;
 
+
+    // Element access
+
         //- Return subscript-checked element.
         inline T& operator()(const label i, const label j);
 
         //- Return const subscript-checked element.
         inline const T& operator()(const label i, const label j) const;
 
-        //- Return as List<Container>
-        List<Container> operator()() const;
 
-        //- Assignment of all entries to the given value
-        inline void operator=(const T& val);
+    // Reading/writing
 
-        //- Copy assignment
-        inline void operator=(const CompactListList<T, Container>& lst);
+        //- Read CompactListList as offsets/values pair from Istream,
+        //- discards current list contents
+        Istream& readList(Istream& is);
 
-        //- Move assignment
-        inline void operator=(CompactListList<T, Container>&& lst);
+        //- Write CompactListList as offsets/values pair
+        Ostream& writeList(Ostream& os, const label shortLen=0) const;
 
 
     // IO Operators
 
-        //- Read CompactListList from Istream, discarding contents
-        //  of existing CompactListList.
-        friend Istream& operator>> <T, Container>
+        //- Read CompactListList offsets/values pair from Istream,
+        //- discarding existing contents
+        friend Istream& operator>> <T>
         (
             Istream&,
-            CompactListList<T, Container>&
+            CompactListList<T>&
         );
 
-        // Write CompactListList to Ostream.
-        friend Ostream& operator<< <T, Container>
+        //- Write CompactListList as offsets/values pair
+        friend Ostream& operator<< <T>
         (
             Ostream&,
-            const CompactListList<T, Container>&
+            const CompactListList<T>&
         );
+
+
+    // Housekeeping
+
+        //- Const access to the packed matrix of values
+        const List<T>& m() const noexcept { return values_; }
+
+        //- Non-const access to the packed matrix of values
+        List<T>& m() noexcept { return values_; }
+
+        //- Return flat index into packed values
+        label index(const label rowi, const label colj) const
+        {
+            return this->toGlobal(rowi, colj);
+        }
+
+        //- Get column within specified row that corresponds to global index
+        label whichColumn(const label rowi, const label i) const
+        {
+            return this->toLocal(rowi, i);
+        }
 };
 
 
 // Note: uses default Foam::Swap (move construct/assignment)
 
+// * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //
+
+template<class T>
+Istream& operator>>(Istream& is, CompactListList<T>& list)
+{
+    return list.readList(is);
+}
+
+template<class T>
+Ostream& operator<<(Ostream& os, const CompactListList<T>& list)
+{
+    return list.writeList(os, Detail::ListPolicy::short_length<T>::value);
+}
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam
diff --git a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H
index 93444caa32..3325fe37b8 100644
--- a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H
+++ b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H
@@ -29,316 +29,523 @@ License
 #include "ListOps.H"
 #include "SubList.H"
 
-// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+// * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
 
-template<class T, class Container>
-inline Foam::CompactListList<T, Container>::CompactListList()
-:
-    size_(0)
-{}
-
-
-template<class T, class Container>
-inline Foam::CompactListList<T, Container>::CompactListList
-(
-    const label mRows,
-    const label nData
-)
-:
-    size_(mRows),
-    offsets_(mRows+1, 0),
-    m_(nData)
-{}
-
-
-template<class T, class Container>
-inline Foam::CompactListList<T, Container>::CompactListList
-(
-    const label mRows,
-    const label nData,
-    const T& val
-)
-:
-    size_(mRows),
-    offsets_(mRows+1, 0),
-    m_(nData, val)
-{}
-
-
-template<class T, class Container>
-inline Foam::CompactListList<T, Container>::CompactListList
-(
-    const CompactListList<T, Container>& lst
-)
-:
-    size_(lst.size()),
-    offsets_(lst.offsets_),
-    m_(lst.m_)
-{}
-
-
-template<class T, class Container>
-inline Foam::CompactListList<T, Container>::CompactListList
-(
-    CompactListList<T, Container>&& lst
-)
+template<class T>
+inline const Foam::CompactListList<T>& Foam::CompactListList<T>::null()
 {
-    transfer(lst);
+    return NullObjectRef<CompactListList<T>>();
 }
 
 
-template<class T, class Container>
-inline Foam::CompactListList<T, Container>::CompactListList
-(
-    CompactListList<T, Container>& list,
-    bool reuse
-)
-:
-    size_(list.size()),
-    offsets_(list.offsets_, reuse),
-    m_(list.m_, reuse)
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+template<class T>
+inline void Foam::CompactListList<T>::enforceSizeSanity()
 {
-    if (reuse)
+    if (offsets_.size() == 1)
     {
-        list.size_ = 0;
+        offsets_.clear();
+    }
+    if (offsets_.empty())
+    {
+        values_.clear();
     }
 }
 
 
-template<class T, class Container>
-inline Foam::autoPtr<Foam::CompactListList<T, Container>>
-Foam::CompactListList<T, Container>::clone() const
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+template<class T>
+inline Foam::CompactListList<T>::CompactListList
+(
+    const CompactListList<T>& list
+)
+:
+    offsets_(list.offsets_),
+    values_(list.values_)
+{}
+
+
+template<class T>
+inline Foam::CompactListList<T>::CompactListList
+(
+    CompactListList<T>&& list
+)
+:
+    offsets_(std::move(list.offsets_)),
+    values_(std::move(list.values_))
+{}
+
+
+template<class T>
+inline Foam::CompactListList<T>::CompactListList
+(
+    CompactListList<T>& list,
+    bool reuse
+)
+:
+    offsets_(list.offsets_, reuse),
+    values_(list.values_, reuse)
+{}
+
+
+
+template<class T>
+inline Foam::CompactListList<T>::CompactListList
+(
+    const label mRows,
+    const label nVals
+)
+:
+    offsets_(mRows+1, Zero),
+    values_(nVals)
 {
-    return autoPtr<CompactListList<T, Container>>::New(*this);
+    // Optionally: enforceSizeSanity();
+}
+
+
+template<class T>
+inline Foam::CompactListList<T>::CompactListList
+(
+    const label mRows,
+    const label nVals,
+    const Foam::zero
+)
+:
+    offsets_(mRows+1, Zero),
+    values_(nVals, Zero)
+{
+    // Optionally: enforceSizeSanity();
+}
+
+
+template<class T>
+inline Foam::CompactListList<T>::CompactListList
+(
+    const label mRows,
+    const label nVals,
+    const T& val
+)
+:
+    offsets_(mRows+1, Zero),
+    values_(nVals, val)
+{
+    // Optionally: enforceSizeSanity();
+}
+
+
+template<class T>
+inline Foam::autoPtr<Foam::CompactListList<T>>
+Foam::CompactListList<T>::clone() const
+{
+    return autoPtr<CompactListList<T>>::New(*this);
 }
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-template<class T, class Container>
-inline const Foam::CompactListList<T, Container>&
-Foam::CompactListList<T, Container>::null()
+template<class T>
+inline const Foam::labelList& Foam::CompactListList<T>::offsets() const noexcept
 {
-    return NullObjectRef<CompactListList<T, Container>>();
+    return offsets_;
 }
 
 
-template<class T, class Container>
-inline bool Foam::CompactListList<T, Container>::empty() const noexcept
+template<class T>
+inline Foam::labelList& Foam::CompactListList<T>::offsets() noexcept
 {
-    return !size_;
+    return offsets_;
 }
 
 
-template<class T, class Container>
-inline Foam::label Foam::CompactListList<T, Container>::size() const noexcept
+template<class T>
+inline const Foam::List<T>& Foam::CompactListList<T>::values() const noexcept
 {
-    return size_;
+    return values_;
 }
 
 
-template<class T, class Container>
-inline Foam::label Foam::CompactListList<T, Container>::totalSize() const
+template<class T>
+inline Foam::List<T>& Foam::CompactListList<T>::values() noexcept
+{
+    return values_;
+}
+
+
+template<class T>
+inline const T* Foam::CompactListList<T>::cdata() const noexcept
+{
+    return values_.cdata();
+}
+
+
+template<class T>
+inline T* Foam::CompactListList<T>::data() noexcept
+{
+    return values_.data();
+}
+
+
+template<class T>
+inline const char* Foam::CompactListList<T>::cdata_bytes() const noexcept
+{
+    return values_.cdata_bytes();
+}
+
+
+template<class T>
+inline char* Foam::CompactListList<T>::data_bytes() noexcept
+{
+    return values_.data_bytes();
+}
+
+
+template<class T>
+inline std::streamsize Foam::CompactListList<T>::size_bytes() const noexcept
+{
+    return values_.size_bytes();
+}
+
+
+template<class T>
+inline bool Foam::CompactListList<T>::empty() const noexcept
+{
+    return (offsets_.size() <= 1);
+}
+
+
+template<class T>
+inline Foam::label Foam::CompactListList<T>::size() const noexcept
+{
+    const label len = (offsets_.size() - 1);
+    return (len < 1) ? static_cast<label>(0) : len;
+}
+
+
+template<class T>
+inline Foam::labelList Foam::CompactListList<T>::sizes() const
+{
+    return localSizes();
+}
+
+
+template<class T>
+inline Foam::label Foam::CompactListList<T>::totalSize() const
 {
     const label len = (offsets_.size() - 1);
     return (len < 1) ? static_cast<label>(0) : offsets_[len];
 }
 
 
-template<class T, class Container>
-inline const Foam::List<Foam::label>&
-Foam::CompactListList<T, Container>::offsets() const
+template<class T>
+inline Foam::label Foam::CompactListList<T>::maxSize() const
 {
-    return offsets_;
+    return this->maxNonLocalSize(-1);
 }
 
 
-template<class T, class Container>
-inline Foam::List<Foam::label>& Foam::CompactListList<T, Container>::offsets()
+template<class T>
+inline const Foam::labelUList
+Foam::CompactListList<T>::localStarts() const
 {
-    return offsets_;
+    const label len = (offsets_.size() - 1);
+
+    if (len < 1) return labelUList::null();
+
+    return labelList::subList(offsets_, len);
 }
 
 
-template<class T, class Container>
-inline const Foam::List<T>& Foam::CompactListList<T, Container>::m()
-const
+template<class T>
+inline Foam::label Foam::CompactListList<T>::localStart(const label i) const
 {
-    return m_;
+    return offsets_[i];
 }
 
 
-template<class T, class Container>
-inline Foam::List<T>& Foam::CompactListList<T, Container>::m()
+template<class T>
+inline Foam::label Foam::CompactListList<T>::localEnd(const label i) const
 {
-    return m_;
+    return offsets_[i+1];
 }
 
 
-template<class T, class Container>
-inline Foam::label Foam::CompactListList<T, Container>::index
+template<class T>
+inline Foam::label Foam::CompactListList<T>::localSize(const label i) const
+{
+    return offsets_[i+1] - offsets_[i];
+}
+
+
+template<class T>
+inline Foam::UList<T>
+Foam::CompactListList<T>::localList(const label i)
+{
+    return SubList<T>(values_, (offsets_[i+1] - offsets_[i]), offsets_[i]);
+}
+
+
+template<class T>
+inline const Foam::UList<T>
+Foam::CompactListList<T>::localList(const label i) const
+{
+    return SubList<T>(values_, (offsets_[i+1] - offsets_[i]), offsets_[i]);
+}
+
+
+template<class T>
+inline Foam::label Foam::CompactListList<T>::toGlobal
 (
-    const label i,
-    const label j
-) const
-{
-    return offsets_[i] + j;
-}
-
-
-template<class T, class Container>
-inline Foam::label Foam::CompactListList<T, Container>::whichRow(const label i)
-const
-{
-    if (i < 0 || i >= m_.size())
-    {
-        FatalErrorInFunction
-            << "Index " << i << " outside 0.." << m_.size()
-            << abort(FatalError);
-    }
-
-    return findLower(offsets_, i+1);
-}
-
-
-template<class T, class Container>
-inline Foam::label Foam::CompactListList<T, Container>::whichColumn
-(
-    const label row,
+    const label rowi,
     const label i
 ) const
 {
-    return i - index(row, 0);
+    return i + offsets_[rowi];
 }
 
 
-template<class T, class Container>
-inline void Foam::CompactListList<T, Container>::resize(const label mRows)
+template<class T>
+inline Foam::label Foam::CompactListList<T>::toLocal
+(
+    const label rowi,
+    const label i
+) const
 {
-    this->setSize(mRows);
+    const label locali = i - offsets_[rowi];
+
+    if (locali < 0 || i >= offsets_[rowi+1])
+    {
+        FatalErrorInFunction
+            << "Index " << i << " does not belong on row "
+            << rowi << nl << "Offsets:" << offsets_
+            << abort(FatalError);
+    }
+
+    return locali;
 }
 
 
-template<class T, class Container>
-inline void Foam::CompactListList<T, Container>::resize
+template<class T>
+inline Foam::label Foam::CompactListList<T>::findRow(const label i) const
+{
+    return (i < 0 || i >= totalSize()) ? -1 : findLower(offsets_, i+1);
+}
+
+
+template<class T>
+inline Foam::label Foam::CompactListList<T>::whichRow(const label i) const
+{
+    const label rowi = findRow(i);
+
+    if (rowi < 0)
+    {
+        FatalErrorInFunction
+            << "Index " << i << " outside of range" << nl
+            << "Offsets:" << offsets_
+            << abort(FatalError);
+    }
+
+    return rowi;
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::clear()
+{
+    offsets_.clear();
+    values_.clear();
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::resize(const label mRows)
+{
+    if (mRows == 0)
+    {
+        // Clear
+        offsets_.clear();
+        values_.clear();
+    }
+    else if (mRows < size())
+    {
+        // Shrink
+        offsets_.resize(mRows+1);
+        values_.resize(offsets_[mRows]);
+    }
+    else if (mRows > size())
+    {
+        // Grow
+        FatalErrorInFunction
+            << "Cannot be used to extend the list from " << size()
+            << " to " << mRows << nl
+            << "    Please use a different resize() function"
+            << abort(FatalError);
+    }
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::resize
 (
     const label mRows,
-    const label nData
+    const label nVals
 )
 {
-    this->setSize(mRows, nData);
+    offsets_.resize(mRows+1, Zero);
+    values_.resize(nVals);
 }
 
 
-template<class T, class Container>
-inline void Foam::CompactListList<T, Container>::resize
+template<class T>
+inline void Foam::CompactListList<T>::resize_nocopy
 (
     const label mRows,
-    const label nData,
-    const T& t
+    const label nVals
 )
 {
-    this->setSize(mRows, nData, t);
+    offsets_.resize(mRows+1, Zero);
+    values_.resize_nocopy(nVals);
 }
 
 
-template<class T, class Container>
-inline void Foam::CompactListList<T, Container>::resize
+template<class T>
+inline void Foam::CompactListList<T>::resize
 (
-    const labelUList& rowSizes
+    const label mRows,
+    const label nVals,
+    const T& val
 )
 {
-    this->setSize(rowSizes);
+    offsets_.resize(mRows+1, Zero);
+    values_.resize(nVals, val);
+    // Optionally: enforceSizeSanity();
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::setSize(const label mRows)
+{
+    this->resize(mRows);
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::setSize
+(
+    const label mRows,
+    const label nVals
+)
+{
+    this->resize(mRows+1, nVals);
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::setSize
+(
+    const label mRows,
+    const label nVals,
+    const T& val
+)
+{
+    this->resize(mRows+1, nVals, val);
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::setSize
+(
+    const labelUList& listSizes
+)
+{
+    this->resize(listSizes);
 }
 
 
 // * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
 
-template<class T, class Container>
-inline Foam::UList<T> Foam::CompactListList<T, Container>::operator[]
+template<class T>
+inline void Foam::CompactListList<T>::operator=
 (
-    const label i
+    const CompactListList<T>& list
 )
 {
-    const label start = offsets_[i];
-    return UList<T>(m_.begin() + start, offsets_[i+1] - start);
+    if (this == &list)
+    {
+        return;  // Self-assignment is a no-op
+    }
+
+    offsets_ = list.offsets_,
+    values_ = list.values_;
 }
 
 
-template<class T, class Container>
+template<class T>
+inline void Foam::CompactListList<T>::operator=
+(
+    CompactListList<T>&& list
+)
+{
+    if (this == &list)
+    {
+        return;  // Self-assignment is a no-op
+    }
+
+    offsets_.transfer(list.offsets_);
+    values_.transfer(list.values_);
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::operator=(const T& val)
+{
+    values_ = val;
+}
+
+
+template<class T>
+inline void Foam::CompactListList<T>::operator=(const Foam::zero)
+{
+    values_ = Zero;
+}
+
+
+template<class T>
+inline Foam::UList<T>
+Foam::CompactListList<T>::operator[](const label i)
+{
+    return this->localList(i);
+}
+
+
+template<class T>
 inline const Foam::UList<T>
-Foam::CompactListList<T, Container>::operator[]
-(
-    const label i
-) const
+Foam::CompactListList<T>::operator[](const label i) const
 {
-    const label start = offsets_[i];
-    return UList<T>
-    (
-        const_cast<T*>(m_.begin() + start),
-        offsets_[i+1] - start
-    );
+    return this->localList(i);
 }
 
 
-template<class T, class Container>
-inline T& Foam::CompactListList<T, Container>::operator()
+template<class T>
+inline T& Foam::CompactListList<T>::operator()
 (
     const label i,
     const label j
 )
 {
-    return m_[index(i, j)];
+    return values_[toGlobal(i, j)];
 }
 
 
-template<class T, class Container>
-inline const T& Foam::CompactListList<T, Container>::operator()
+template<class T>
+inline const T& Foam::CompactListList<T>::operator()
 (
     const label i,
     const label j
 ) const
 {
-    return m_[index(i, j)];
-}
-
-
-template<class T, class Container>
-inline void Foam::CompactListList<T, Container>::operator=(const T& val)
-{
-    m_ = val;
-}
-
-
-template<class T, class Container>
-inline void Foam::CompactListList<T, Container>::operator=
-(
-    const CompactListList<T, Container>& lst
-)
-{
-    if (this == &lst)
-    {
-        return;  // Self-assignment is a no-op
-    }
-
-    size_ = lst.size_;
-    offsets_ = lst.offsets_,
-    m_ = lst.m_;
-}
-
-
-template<class T, class Container>
-inline void Foam::CompactListList<T, Container>::operator=
-(
-    CompactListList<T, Container>&& lst
-)
-{
-    if (this == &lst)
-    {
-        return;  // Self-assignment is a no-op
-    }
-
-    transfer(lst);
+    return values_[toGlobal(i, j)];
 }
 
 
diff --git a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListIO.C b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListIO.C
index 66127928a0..07f5d25d37 100644
--- a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListIO.C
+++ b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListIO.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2011 OpenFOAM Foundation
+    Copyright (C) 2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -30,40 +30,37 @@ License
 
 // * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * * //
 
-template<class T, class Container>
-Foam::CompactListList<T, Container>::CompactListList(Istream& is)
+template<class T>
+Foam::CompactListList<T>::CompactListList(Istream& is)
+:
+    offsets_(is),
+    values_(is)
 {
-    operator>>(is, *this);
+    // Optionally: enforceSizeSanity();
 }
 
 
 // * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //
 
-template<class T, class Container>
-Foam::Istream& Foam::operator>>(Istream& is, CompactListList<T, Container>& lst)
+template<class T>
+Foam::Istream& Foam::CompactListList<T>::readList(Istream& is)
 {
-    is  >> lst.offsets_ >> lst.m_;
-    // Note: empty list gets output as two empty lists
-    if (lst.offsets_.size())
-    {
-        lst.size_ = lst.offsets_.size()-1;
-    }
-    else
-    {
-        lst.size_ = 0;
-    }
+    offsets_.readList(is);
+    values_.readList(is);
+    // Optionally: enforceSizeSanity();
     return is;
 }
 
 
-template<class T, class Container>
-Foam::Ostream& Foam::operator<<
+template<class T>
+Foam::Ostream& Foam::CompactListList<T>::writeList
 (
     Ostream& os,
-    const CompactListList<T, Container>& lst
-)
+    const label shortLen
+) const
 {
-    os  << lst.offsets_ << lst.m_;
+    offsets_.writeList(os, shortLen);
+    values_.writeList(os, shortLen);
     return os;
 }
 
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndex.C b/src/OpenFOAM/parallel/globalIndex/globalIndex.C
index 969e7602e0..518602a8ea 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndex.C
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndex.C
@@ -128,28 +128,29 @@ Foam::globalIndex::globalIndex(Istream& is)
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-void Foam::globalIndex::bin
+Foam::CompactListList<Foam::label>
+Foam::globalIndex::bin
 (
     const labelUList& offsets,
     const labelUList& globalIds,
     labelList& order,
-    CompactListList<label>& bins,
     DynamicList<label>& validBins
 )
 {
     sortedOrder(globalIds, order);
-
-    bins.m() = UIndirectList<label>(globalIds, order);
-
-    labelList& binOffsets = bins.offsets();
-    binOffsets.resize_nocopy(offsets.size());
-    binOffsets = Zero;
-
     validBins.clear();
 
+    CompactListList<label> bins;
+
     if (globalIds.size())
     {
-        const label id = bins.m()[0];
+        labelList& binOffsets = bins.offsets();
+        binOffsets.resize(offsets.size(), Zero);
+
+        labelList& binValues = bins.values();
+        binValues = UIndirectList<label>(globalIds, order);
+
+        const label id = binValues[0];
         label proci = findLower(offsets, id+1);
 
         validBins.append(proci);
@@ -157,7 +158,7 @@ void Foam::globalIndex::bin
 
         for (label i = 1; i < order.size(); i++)
         {
-            const label id = bins.m()[i];
+            const label id = binValues[i];
 
             if (id < offsets[proci+1])
             {
@@ -185,6 +186,8 @@ void Foam::globalIndex::bin
             binOffsets[j] = binOffsets[proci]+binSize;
         }
     }
+
+    return bins;
 }
 
 
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndex.H b/src/OpenFOAM/parallel/globalIndex/globalIndex.H
index a32c2d08ee..f32eef6b39 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndex.H
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndex.H
@@ -76,12 +76,12 @@ class globalIndex
     // Private Member Functions
 
         //- Sort and bin. validBins contains bins with non-zero size.
-        static void bin
+        static CompactListList<label>
+        bin
         (
             const labelUList& offsets,
             const labelUList& globalIds,
             labelList& order,
-            CompactListList<label>& sortedElems,
             DynamicList<label>& validBins
         );
 
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
index 5634d802e3..a653d34fac 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
@@ -840,19 +840,16 @@ void Foam::globalIndex::get
 ) const
 {
     allFld.resize_nocopy(globalIds.size());
+
     if (globalIds.size())
     {
         // Sort according to processor
         labelList order;
-        CompactListList<label> bins;
         DynamicList<label> validBins(Pstream::nProcs());
-        bin
+
+        CompactListList<label> bins
         (
-            offsets(),
-            globalIds,
-            order,
-            bins,
-            validBins
+            bin(offsets(), globalIds, order, validBins)
         );
 
         // Send local indices to individual processors as local index
@@ -860,12 +857,11 @@ void Foam::globalIndex::get
 
         for (const auto proci : validBins)
         {
-            const labelUList& es = bins[proci];
+            labelList localIDs(bins[proci]);
 
-            labelList localIDs(es.size());
-            forAll(es, i)
+            for (label& val : localIDs)
             {
-                localIDs[i] = toLocal(proci, es[i]);
+                val = toLocal(proci, val);
             }
 
             UOPstream os(proci, sendBufs);
diff --git a/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C b/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C
index 24c4a537c1..044a935d90 100644
--- a/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C
+++ b/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2018 OpenFOAM Foundation
-    Copyright (C) 2015-2021 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -1702,7 +1702,8 @@ void Foam::fvMeshDistribute::sendMesh
     // Send
     toDomain
         << mesh.points()
-        << CompactListList<label, face>(mesh.faces())
+        // Send as (offsets/values)
+        << CompactListList<label>::pack<face>(mesh.faces())
         << mesh.faceOwner()
         << mesh.faceNeighbour()
         << mesh.boundaryMesh()
@@ -1744,7 +1745,8 @@ Foam::autoPtr<Foam::fvMesh> Foam::fvMeshDistribute::receiveMesh
 )
 {
     pointField domainPoints(fromNbr);
-    faceList domainFaces = CompactListList<label, face>(fromNbr)();
+    // Receive as (offsets/values), unpack to faceList
+    faceList domainFaces = CompactListList<label>(fromNbr).unpack<face>();
     labelList domainAllOwner(fromNbr);
     labelList domainAllNeighbour(fromNbr);
     PtrList<entry> patchEntries(fromNbr);
diff --git a/src/meshTools/polyTopoChange/polyTopoChange.C b/src/meshTools/polyTopoChange/polyTopoChange.C
index 9b0803595b..58a49e98dd 100644
--- a/src/meshTools/polyTopoChange/polyTopoChange.C
+++ b/src/meshTools/polyTopoChange/polyTopoChange.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2021 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -37,6 +37,7 @@ License
 #include "polyAddCell.H"
 #include "polyModifyCell.H"
 #include "polyRemoveCell.H"
+#include "CompactListList.H"
 #include "objectMap.H"
 #include "processorPolyPatch.H"
 #include "ListOps.H"
@@ -572,8 +573,8 @@ void Foam::polyTopoChange::makeCellCells
         if (nei >= 0)
         {
             label own = faceOwner_[facei];
-            cellCells.m()[cellCells.index(own, nNbrs[own]++)] = nei;
-            cellCells.m()[cellCells.index(nei, nNbrs[nei]++)] = own;
+            cellCells(own, nNbrs[own]++) = nei;
+            cellCells(nei, nNbrs[nei]++) = own;
         }
     }
 }
diff --git a/src/meshTools/polyTopoChange/polyTopoChange.H b/src/meshTools/polyTopoChange/polyTopoChange.H
index 98c74ebdfb..9ad146d575 100644
--- a/src/meshTools/polyTopoChange/polyTopoChange.H
+++ b/src/meshTools/polyTopoChange/polyTopoChange.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2018-2021 OpenCFD Ltd.
+    Copyright (C) 2018-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -68,7 +68,6 @@ SourceFiles
 
 #include "DynamicList.H"
 #include "labelList.H"
-#include "CompactListList.H"
 #include "pointField.H"
 #include "Map.H"
 #include "HashSet.H"
@@ -92,6 +91,7 @@ class topoAction;
 class objectMap;
 class IOobject;
 class mapPolyMesh;
+template<class T> class CompactListList;
 
 /*---------------------------------------------------------------------------*\
                        Class polyTopoChange Declaration
diff --git a/src/parallel/decompose/decompose/decompositionInformation.C b/src/parallel/decompose/decompose/decompositionInformation.C
index c23ffccf62..ba3bc31a2c 100644
--- a/src/parallel/decompose/decompose/decompositionInformation.C
+++ b/src/parallel/decompose/decompose/decompositionInformation.C
@@ -143,7 +143,7 @@ Foam::decompositionInformation::decompositionInformation
     distrib_(),
     nDomains_(0)
 {
-    populate(cellCells.m(), cellCells.offsets(), decomp, nDomains);
+    populate(cellCells.values(), cellCells.offsets(), decomp, nDomains);
 }
 
 
diff --git a/src/parallel/decompose/decompose/decompositionInformation.H b/src/parallel/decompose/decompose/decompositionInformation.H
index e50fe4c0df..ef1c9caa19 100644
--- a/src/parallel/decompose/decompose/decompositionInformation.H
+++ b/src/parallel/decompose/decompose/decompositionInformation.H
@@ -120,20 +120,18 @@ public:
 
 
     //- Destructor
-    ~decompositionInformation()
-    {}
+    ~decompositionInformation() = default;
 
 
     // Member Functions
 
         void clear();
 
-        label nDomains() const
+        label nDomains() const noexcept
         {
             return nDomains_;
         }
 
-
         void printSummary(Ostream& os) const;
 
         void printDetails(Ostream& os) const;
diff --git a/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C b/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C
index c591103428..588a233c99 100644
--- a/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C
+++ b/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C
@@ -414,7 +414,7 @@ Foam::labelList Foam::decompositionMethod::decompose
     (
         decompose
         (
-            coarseCellCells(),
+            coarseCellCells.unpack(),
             coarsePoints,
             coarseWeights
         )
diff --git a/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C b/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C
index 71e894e644..48636a9a0c 100644
--- a/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C
+++ b/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C
@@ -233,7 +233,13 @@ Foam::labelList Foam::metisLikeDecomp::decompose
 
     // Decompose using default weights
     labelList decomp;
-    decomposeGeneral(cellCells.m(), cellCells.offsets(), pointWeights, decomp);
+    decomposeGeneral
+    (
+        cellCells.values(),
+        cellCells.offsets(),
+        pointWeights,
+        decomp
+    );
 
     return decomp;
 }
@@ -271,7 +277,13 @@ Foam::labelList Foam::metisLikeDecomp::decompose
 
     // Decompose using default weights
     labelList decomp;
-    decomposeGeneral(cellCells.m(), cellCells.offsets(), agglomWeights, decomp);
+    decomposeGeneral
+    (
+        cellCells.values(),
+        cellCells.offsets(),
+        agglomWeights,
+        decomp
+    );
 
 
     // Rework back into decomposition for original mesh
@@ -305,11 +317,18 @@ Foam::labelList Foam::metisLikeDecomp::decompose
     //   adjncy      : contains neighbours (= edges in graph)
     //   xadj(celli) : start of information in adjncy for celli
 
-    CompactListList<label> cellCells(globalCellCells);
+
+    auto cellCells(CompactListList<label>::pack(globalCellCells));
 
     // Decompose using default weights
     labelList decomp;
-    decomposeGeneral(cellCells.m(), cellCells.offsets(), cellWeights, decomp);
+    decomposeGeneral
+    (
+        cellCells.values(),
+        cellCells.offsets(),
+        cellWeights,
+        decomp
+    );
 
     return decomp;
 }
diff --git a/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C b/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
index c04abe54df..6558aa84da 100644
--- a/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
+++ b/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2017-2021 OpenCFD Ltd.
+    Copyright (C) 2017-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -614,7 +614,7 @@ Foam::labelList Foam::multiLevelDecomp::decompose
 
     decompose
     (
-        cellCells(),
+        cellCells.unpack(),
         cc,
         cWeights,
         cellMap,      // map back to original cells
diff --git a/src/parallel/decompose/ptscotchDecomp/ptscotchDecomp.C b/src/parallel/decompose/ptscotchDecomp/ptscotchDecomp.C
index 9f73443ff8..b494548e1b 100644
--- a/src/parallel/decompose/ptscotchDecomp/ptscotchDecomp.C
+++ b/src/parallel/decompose/ptscotchDecomp/ptscotchDecomp.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2021 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -516,7 +516,7 @@ Foam::labelList Foam::ptscotchDecomp::decompose
     labelList decomp;
     decompose
     (
-        cellCells.m(),
+        cellCells.values(),
         cellCells.offsets(),
         pointWeights,
         decomp
@@ -563,7 +563,7 @@ Foam::labelList Foam::ptscotchDecomp::decompose
     labelList decomp;
     decompose
     (
-        cellCells.m(),
+        cellCells.values(),
         cellCells.offsets(),
         pointWeights,
         decomp
@@ -604,13 +604,13 @@ Foam::labelList Foam::ptscotchDecomp::decompose
     //   adjncy      : contains neighbours (= edges in graph)
     //   xadj(celli) : start of information in adjncy for celli
 
-    CompactListList<label> cellCells(globalCellCells);
+    auto cellCells(CompactListList<label>::pack(globalCellCells));
 
     // Decompose using weights
     labelList decomp;
     decompose
     (
-        cellCells.m(),
+        cellCells.values(),
         cellCells.offsets(),
         cWeights,
         decomp
diff --git a/src/renumber/renumberMethods/CuthillMcKeeRenumber/CuthillMcKeeRenumber.C b/src/renumber/renumberMethods/CuthillMcKeeRenumber/CuthillMcKeeRenumber.C
index 394b4ec8a7..d404f93dae 100644
--- a/src/renumber/renumberMethods/CuthillMcKeeRenumber/CuthillMcKeeRenumber.C
+++ b/src/renumber/renumberMethods/CuthillMcKeeRenumber/CuthillMcKeeRenumber.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -79,7 +79,7 @@ Foam::labelList Foam::CuthillMcKeeRenumber::renumber
         cellCells
     );
 
-    labelList orderedToOld = bandCompression(cellCells());
+    labelList orderedToOld = bandCompression(cellCells.unpack());
 
     if (reverse_)
     {
diff --git a/src/renumber/renumberMethods/renumberMethod/renumberMethod.C b/src/renumber/renumberMethods/renumberMethod/renumberMethod.C
index bdf3f4af30..934c04c19c 100644
--- a/src/renumber/renumberMethods/renumberMethod/renumberMethod.C
+++ b/src/renumber/renumberMethods/renumberMethod/renumberMethod.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2019-2021 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -85,7 +85,7 @@ Foam::labelList Foam::renumberMethod::renumber
     );
 
     // Renumber based on agglomerated points
-    return renumber(cellCells(), points);
+    return renumber(cellCells.unpack(), points);
 }
 
 
@@ -123,7 +123,7 @@ Foam::labelList Foam::renumberMethod::renumber
     (
         renumber
         (
-            coarseCellCells(),
+            coarseCellCells.unpack(),
             coarsePoints
         )
     );
diff --git a/src/renumber/renumberMethods/renumberMethod/renumberMethod.H b/src/renumber/renumberMethods/renumberMethod/renumberMethod.H
index 5ab880b40c..46dc5d4346 100644
--- a/src/renumber/renumberMethods/renumberMethod/renumberMethod.H
+++ b/src/renumber/renumberMethods/renumberMethod/renumberMethod.H
@@ -50,16 +50,14 @@ namespace Foam
 
 class renumberMethod
 {
-
 protected:
 
-    // Protected data
+    // Protected Data
 
         const dictionary& renumberDict_;
 
-private:
 
-    // Private Member Functions
+    // Protected Member Functions
 
         //- No copy construct
         renumberMethod(const renumberMethod&) = delete;
@@ -118,7 +116,7 @@ public:
         virtual labelList renumber(const pointField&) const
         {
             NotImplemented;
-            return labelList(0);
+            return labelList();
         }
 
         //- Return the order in which cells need to be visited, i.e.
diff --git a/src/renumber/renumberMethods/springRenumber/springRenumber.C b/src/renumber/renumberMethods/springRenumber/springRenumber.C
index 265ec9866f..9078f4bc3e 100644
--- a/src/renumber/renumberMethods/springRenumber/springRenumber.C
+++ b/src/renumber/renumberMethods/springRenumber/springRenumber.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -75,7 +75,7 @@ Foam::labelList Foam::springRenumber::renumber
         cellCells
     );
 
-    return renumber(cellCells(), points);
+    return renumber(cellCells.unpack(), points);
 }