From dd9ecd4988d0f7b1b000c57f44f84a6dc735b054 Mon Sep 17 00:00:00 2001
From: Mark Olesen <Mark.Olesen@esi-group.com>
Date: Wed, 8 Aug 2018 23:54:27 +0200
Subject: [PATCH] ENH: add missing Hash function for List/UList (issue #966)

- there were previously no hashing mechanisms for lists so they
  would fall back to the definition for primitives and hash the
  memory location of the allocated List object.

- provide a UList::Hash<> sub-class for inheritance, and also a global
  specialization for UList<T>, List<T> such that the hash value for
  List<List<T>> cascades properly.

- provide similar function in triFace to ensure that it remains
  similar in behaviour to face.

- added SymmHash to Pair, for use when order is unimportant.

STYLE: use string::hash() more consistently

- no particular reason to use Hash<word>() which forwards to
  string::hash() anyhow
---
 .../multiphaseSystem/multiphaseSystem.H       |  13 +-
 .../phasesSystem/phaseSystem/phaseSystem.H    |   3 +-
 applications/test/FixedList/Test-FixedList.C  |   7 +-
 applications/test/Hashing/Test-Hashing.C      | 313 +++++++++++++-----
 applications/test/Hashing/hashingTests        |  42 +++
 applications/test/List/Test-List.C            |  14 +
 .../ideasUnvToFoam/ideasUnvToFoam.C           |  25 +-
 .../netgenNeutralToFoam/netgenNeutralToFoam.C |   9 +-
 .../containers/Lists/FixedList/FixedList.H    |  72 +++-
 .../containers/Lists/FixedList/FixedListI.H   |  28 --
 src/OpenFOAM/containers/Lists/List/List.H     |  24 ++
 src/OpenFOAM/containers/Lists/UList/UList.H   |  55 ++-
 src/OpenFOAM/containers/Lists/UList/UListI.H  |   1 +
 src/OpenFOAM/meshes/meshShapes/edge/edge.H    |  91 ++---
 src/OpenFOAM/meshes/meshShapes/face/face.H    |  30 +-
 .../meshes/meshShapes/triFace/triFace.H       |  77 +++--
 .../processorCyclicPolyPatch.C                |   4 +-
 src/OpenFOAM/primitives/Pair/Pair.H           |  61 +++-
 src/OpenFOAM/primitives/hashes/Hash/Hash.H    |  92 ++---
 src/OpenFOAM/primitives/hashes/Hash/HashFwd.H |  46 +++
 .../primitives/hashes/Hasher/Hasher.H         |  20 +-
 .../surface/cuttingPlane/cuttingPlane.C       |  29 +-
 src/surfMesh/surfaceFormats/obj/OBJstream.H   |   1 -
 23 files changed, 712 insertions(+), 345 deletions(-)
 create mode 100644 src/OpenFOAM/primitives/hashes/Hash/HashFwd.H

diff --git a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/multiphaseSystem/multiphaseSystem.H b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/multiphaseSystem/multiphaseSystem.H
index 068d25961b..ef63221ac7 100644
--- a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/multiphaseSystem/multiphaseSystem.H
+++ b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/multiphaseSystem/multiphaseSystem.H
@@ -54,20 +54,13 @@ class multiphaseSystem
 {
 protected:
 
-        typedef
-            HashTable
-            <
-                volScalarField::Internal,
-                word,
-                word::hash
-            >
-            SuSpTable;
+        typedef HashTable<volScalarField::Internal> SuSpTable;
 
         typedef HashTable<scalar, phasePairKey, phasePairKey::hash>
             scalarTable;
 
-        typedef HashTable<surfaceScalarField, word, word::hash>
-            compressionFluxTable;
+        typedef HashTable<surfaceScalarField> compressionFluxTable;
+
 
     // Protected data
 
diff --git a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/phaseSystem.H b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/phaseSystem.H
index ad0dc154d0..031587beeb 100644
--- a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/phaseSystem.H
+++ b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/phasesSystem/phaseSystem/phaseSystem.H
@@ -75,8 +75,7 @@ public:
             phasePairTable;
 
 
-        typedef
-            HashTable<autoPtr<phaseModel>, word, word::hash> phaseModelTable;
+        typedef HashTable<autoPtr<phaseModel>> phaseModelTable;
 
 
 protected:
diff --git a/applications/test/FixedList/Test-FixedList.C b/applications/test/FixedList/Test-FixedList.C
index 1e3703b2b8..0b5cff8374 100644
--- a/applications/test/FixedList/Test-FixedList.C
+++ b/applications/test/FixedList/Test-FixedList.C
@@ -139,13 +139,16 @@ int main(int argc, char *argv[])
         FixedList<label, 4> list1{2, 3, 4, 5};
 
         Info<< "list1:" << list1
-            << " hash:" << FixedList<label, 4>::Hash<>()(list1) << nl;
+            << " hash:" << FixedList<label,4>::Hash<>()(list1) << nl
+            << " hash:" << Hash<FixedList<label,4>>()(list1) << nl;
 
         label a[4] = {0, 1, 2, 3};
         FixedList<label, 4> list2(a);
 
         Info<< "list2:" << list2
-            << " hash:" << FixedList<label, 4>::Hash<>()(list2) << nl;
+            << " hash:" << FixedList<label,4>::Hash<>()(list2) << nl
+            << " hash:" << Hash<FixedList<label,4>>()(list2) << nl;
+
 
         // Using FixedList for content too
         {
diff --git a/applications/test/Hashing/Test-Hashing.C b/applications/test/Hashing/Test-Hashing.C
index 4461679d08..da3688481a 100644
--- a/applications/test/Hashing/Test-Hashing.C
+++ b/applications/test/Hashing/Test-Hashing.C
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -36,6 +36,7 @@ Description
 #include "labelList.H"
 #include "labelPair.H"
 #include "edgeList.H"
+#include "faceList.H"
 #include "triFaceList.H"
 
 #include "Hash.H"
@@ -50,7 +51,7 @@ void infoHashString
 {
     if (modulus)
     {
-        Info<< "basic string hashing (mod " << label(modulus) << ")" << endl;
+        Info<< "basic string hashing (mod " << label(modulus) << ")" << nl;
 
         for (const auto& str : lst)
         {
@@ -72,6 +73,190 @@ void infoHashString
 }
 
 
+
+void reportHashList(const UList<string>& list)
+{
+    Info<< "contiguous = " << contiguous<string>() << nl << nl;
+
+    for (const string& val : list)
+    {
+        unsigned hash1 = string::hash()(val);
+
+        Info<< hex << hash1 << ": " << val << nl;
+    }
+}
+
+
+void reportHashList(const UList<label>& list)
+{
+    Info<<"contiguous = " << contiguous<label>() << nl << nl;
+
+    for (const label val : list)
+    {
+        // Direct value
+        unsigned hash1 = Hash<label>()(val);
+
+        // Hashed byte-wise
+        unsigned hash2 = Hash<label>()(val, 0);
+
+        Info<< hex << hash1
+            << " (seeded: " << hash2 << ")"
+            << ": " << dec << val << nl;
+    }
+}
+
+
+void reportHashList(const UList<face>& list)
+{
+    Info<<"contiguous = " << contiguous<label>() << nl << nl;
+
+    for (const face& f : list)
+    {
+        // Direct value
+        unsigned hash1 = face::Hash<>()(f);
+
+        unsigned hash2 = Hash<face>()(f);
+
+        Info<< hex << "face::Hash<> " << hash1
+            << " Hash<face> " << hash2
+            << ": " << dec << flatOutput(f) << nl;
+    }
+}
+
+
+void reportHashList(const UList<labelList>& list)
+{
+    for (const labelList& val : list)
+    {
+        unsigned hash1 = Hasher
+        (
+            val.cdata(),
+            val.size() * sizeof(label)
+        );
+
+        unsigned hash2 = Hash<labelList>()(val);
+        unsigned hash2b = labelList::Hash<>()(val);
+
+        Info<< hex << hash1 << " or " << hash2
+            << "(" << hash2b << ") "
+            << ": " << dec << val << nl;
+    }
+
+    unsigned hash2 = Hash<labelListList>()(list);
+    unsigned hash2bad = HasherT(list);
+
+    Info<< hex << hash2 << " : " << dec << flatOutput(list) << nl
+        << hex << hash2bad << " as direct hash would be wrong"
+        << dec << nl;
+}
+
+
+typedef Pair<word> wordPair;
+
+void reportHashList(const UList<wordPair>& list)
+{
+    Info<<"contiguous = " << contiguous<wordPair>() << nl << nl;
+
+    for (const wordPair& pr : list)
+    {
+        unsigned hash1 = Hash<wordPair>()(pr);
+
+        // as FixedList
+        unsigned hash2 = wordPair::Hash<>()(pr);
+
+        // as FixedList
+        unsigned hash2sym = wordPair::SymmHash<>()(pr);
+
+        // as FixedList
+        unsigned hash3 = Hash<FixedList<word,2>>()(pr);
+
+        Info<< hex << hash1 << " (as FixedList: " << hash2
+            << ") or " << hash3
+            << " symm-hash:" << hash2sym
+            << " : "<< dec << flatOutput(pr) << nl;
+    }
+}
+
+
+void reportHashList(const UList<labelPair>& list)
+{
+    Info<<"contiguous = " << contiguous<labelPair>() << nl << nl;
+
+    for (const labelPair& pr : list)
+    {
+        unsigned hash1 = Hash<labelPair>()(pr);
+
+        // as FixedList
+        unsigned hash2 = labelPair::Hash<>()(pr);
+
+        // as FixedList
+        unsigned hash3 = Hash<labelPair>()(pr);
+
+        Info<< hex << hash1 << " (as FixedList: " << hash2
+            << ") or " << hash3
+            << " : "<< dec << pr << nl;
+    }
+}
+
+
+void reportHashList(const UList<labelPairPair>& list)
+{
+    Info<<"contiguous = " << contiguous<labelPairPair>() << nl << nl;
+
+    for (const labelPairPair& pr : list)
+    {
+        unsigned hash1 = Hash<labelPairPair>()(pr);
+
+        // as FixedList
+        unsigned hash2 = labelPairPair::Hash<>()(pr);
+
+        // as FixedList
+        unsigned hash3 = Hash<labelPairPair>()(pr);
+
+        Info<< hex << hash1 << " (as FixedList: " << hash2
+            << ") or " << hash3
+            << " : "<< dec << pr << nl;
+    }
+}
+
+
+void reportHashList(const UList<edge>& list)
+{
+    Info<<"contiguous = " << contiguous<edge>() << nl << nl;
+
+    for (const edge& e : list)
+    {
+        unsigned hash1 = Hash<edge>()(e);
+
+        // as FixedList
+        unsigned hash2 = labelPair::Hash<>()(e);
+
+        // as FixedList
+        unsigned hash3 = Hash<labelPair>()(e);
+
+        Info<< hex << hash1 << " (as FixedList: " << hash2
+            << ") or " << hash3
+            << " : "<< dec << e << nl;
+    }
+}
+
+
+void reportHashList(const UList<triFace>& list)
+{
+    Info<<"contiguous = " << contiguous<triFace>() << nl << nl;
+
+    for (const triFace& f : list)
+    {
+        // direct value
+        unsigned hash1 = Hash<triFace>()(f);
+        unsigned hash2 = FixedList<label, 3>::Hash<>()(f);
+
+        Info<< hex << hash1 << " (as FixedList: " << hash2
+            << "): " << dec << f << nl;
+    }
+}
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 //  Main program:
 
@@ -81,114 +266,74 @@ int main(int argc, char *argv[])
 
     IFstream is("hashingTests");
 
+    if (!is.good())
+    {
+        Info<< "No \"hashingTests\" file found ...\n";
+    }
+
     while (is.good())
     {
         const word listType(is);
 
-        Info<< endl;
-        IOobject::writeDivider(Info) << listType << endl;
+        if (listType.empty()) continue;
+
+        Info<< nl;
+        IOobject::writeDivider(Info) << listType << nl;
 
         if (listType == "stringList")
         {
-            Info<< "contiguous = " << contiguous<string>() << endl << endl;
-
-            stringList lst(is);
-
-            forAll(lst, i)
-            {
-                unsigned hash1 = string::hash()(lst[i]);
-
-                Info<< hex << hash1 << ": " << lst[i] << endl;
-            }
+            stringList list(is);
 
+            reportHashList(list);
         }
         else if (listType == "labelList")
         {
-            Info<<"contiguous = " << contiguous<label>() << endl << endl;
-
-            labelList lst(is);
-
-            forAll(lst, i)
-            {
-                // direct value
-                unsigned hash1 = Hash<label>()(lst[i]);
-
-                // hashed byte-wise
-                unsigned hash2 = Hash<label>()(lst[i], 0);
-
-                Info<< hex << hash1
-                    << " (seeded: " << hash2 << ")"
-                    << ": " << dec << lst[i] << endl;
-            }
-
-            if (contiguous<label>())
-            {
-                unsigned hash3 = Hasher
-                (
-                    lst.cdata(),
-                    lst.size() * sizeof(label)
-                );
-
-                Info<<"contiguous hashed value " << hex << hash3 << endl;
-            }
+            labelList list(is);
+            reportHashList(list);
+        }
+        else if (listType == "faceList")
+        {
+            faceList list(is);
+            reportHashList(list);
         }
         else if (listType == "labelListList")
         {
-            List<List<label>> lst(is);
-
-            forAll(lst, i)
-            {
-                unsigned hash1 = Hasher
-                (
-                    lst[i].cdata(),
-                    lst[i].size() * sizeof(label)
-                );
-
-                Info<< hex << hash1
-                    << ": " << dec << lst[i] << endl;
-            }
-
+            List<labelList> list(is);
+            reportHashList(list);
+        }
+        else if (listType == "wordPairList")
+        {
+            List<wordPair> list(is);
+            reportHashList(list);
+        }
+        else if (listType == "labelPairList")
+        {
+            labelPairList list(is);
+            reportHashList(list);
+        }
+        else if (listType == "labelPairPairList")
+        {
+            List<labelPairPair> list(is);
+            reportHashList(list);
         }
         else if (listType == "edgeList")
         {
-            Info<<"contiguous = " << contiguous<edge>() << endl << endl;
-
-            edgeList lst(is);
-
-            forAll(lst, i)
-            {
-                unsigned hash1 = Hash<edge>()(lst[i]);
-
-                // as FixedList
-                unsigned hash2 = labelPair::Hash<>()(lst[i]);
-
-                Info<< hex << hash1 << " (as FixedList: " << hash2
-                    << "): " << dec << lst[i] << endl;
-            }
+            edgeList list(is);
+            reportHashList(list);
         }
         else if (listType == "triFaceList")
         {
-            Info<<"contiguous = " << contiguous<triFace>() << endl << endl;
-
-            triFaceList lst(is);
-
-            forAll(lst, i)
-            {
-                // direct value
-                unsigned hash1 = Hash<triFace>()(lst[i]);
-                unsigned hash2 = FixedList<label, 3>::Hash<>()(lst[i]);
-
-                Info<< hex << hash1 << " (as FixedList: " << hash2
-                    << "): " << dec << lst[i] << endl;
-            }
+            triFaceList list(is);
+            reportHashList(list);
         }
         else
         {
-            Info<< "unknown type: " << listType << endl;
+            Info<< "unknown type: " << listType << nl;
         }
-
     }
 
+    Info<< "\nEnd\n" << nl;
+
     return 0;
 }
 
diff --git a/applications/test/Hashing/hashingTests b/applications/test/Hashing/hashingTests
index 5fde9c5191..6702beccb1 100644
--- a/applications/test/Hashing/hashingTests
+++ b/applications/test/Hashing/hashingTests
@@ -24,6 +24,7 @@ labelList
     -1
     -10
     -100
+    100
 )
 
 labelListList
@@ -34,6 +35,16 @@ labelListList
     (0 1)
     (100 1000)
     (0 1 100 1000)
+    (100 1000)
+)
+
+faceList
+(
+    (0 1 2 3 4 5)
+    (5 4 3 1 2 0)
+    (0 1 2 3 4 5)
+    (100 0 15)
+    (15 0 100)
 )
 
 // edges are hashed commutatively
@@ -45,6 +56,7 @@ edgeList
     (100 45)
     (128 1000)
     (1000 128)
+    (100 45)
 )
 
 // triFaces are also hashed commutatively (via multiply/add)
@@ -56,4 +68,34 @@ triFaceList
 )
 
 
+labelPairList
+(
+    (0 1)
+    (1 0)
+    (45 100)
+    (100 45)
+    (128 1000)
+    (1000 128)
+    (100 45)
+)
+
+
+labelPairPairList
+(
+    ((0 1) (1 0))
+    ((45 100) (100 45))
+    ((128 1000) (1000 128))
+    ((45 100) (100 45))
+)
+
+
+wordPairList
+(
+    ("Yes" "No")
+    ("True" "False")
+    ("No" "Yes")
+    ("False" "True")
+)
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
diff --git a/applications/test/List/Test-List.C b/applications/test/List/Test-List.C
index 95b800de93..5ec2bab843 100644
--- a/applications/test/List/Test-List.C
+++ b/applications/test/List/Test-List.C
@@ -598,6 +598,20 @@ int main(int argc, char *argv[])
         << "-wordList:   " << flatOutput(wLst)  << nl
         << "-stringList: " << flatOutput(sLst)  << endl;
 
+    // Hash values
+    {
+        labelList list1(identity(5));
+        labelList list2(identity(5));
+
+        Info<<"hash of " << flatOutput(list1)
+            << " = " << Hash<labelList>()(list1) << " or "
+            << labelList::Hash<>()(list1) << nl;
+
+        Info<<"hash of " << flatOutput(list2) << " = "
+            << Hash<labelList>()(list2) << " or "
+            << labelList::Hash<>()(list2) << nl;
+    }
+
     return 0;
 }
 
diff --git a/applications/utilities/mesh/conversion/ideasUnvToFoam/ideasUnvToFoam.C b/applications/utilities/mesh/conversion/ideasUnvToFoam/ideasUnvToFoam.C
index 19f1b06d32..44b607c3f7 100644
--- a/applications/utilities/mesh/conversion/ideasUnvToFoam/ideasUnvToFoam.C
+++ b/applications/utilities/mesh/conversion/ideasUnvToFoam/ideasUnvToFoam.C
@@ -54,24 +54,8 @@ using namespace Foam;
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-namespace Foam
-{
-    template<>
-    inline unsigned Hash<face>::operator()(const face& t, unsigned seed) const
-    {
-        return Hasher(t.cdata(),t.size()*sizeof(label), seed);
-    }
-
-    template<>
-    inline unsigned Hash<face>::operator()(const face& t) const
-    {
-        return Hash<face>::operator()(t, 0);
-    }
-}
-
 const string SEPARATOR("    -1");
 
-
 bool isSeparator(const std::string& line)
 {
     return line.substr(0, 6) == SEPARATOR;
@@ -861,7 +845,7 @@ int main(int argc, char *argv[])
     Map<label> faceToCell[2];
 
     {
-        HashTable<label, face, Hash<face>> faceToFaceID(boundaryFaces.size());
+        HashTable<label, face, face::Hash<>> faceToFaceID(boundaryFaces.size());
         forAll(boundaryFaces, facei)
         {
             SortableList<label> sortedVerts(boundaryFaces[facei]);
@@ -874,12 +858,11 @@ int main(int argc, char *argv[])
             forAll(faces, i)
             {
                 SortableList<label> sortedVerts(faces[i]);
-                HashTable<label, face, Hash<face>>::const_iterator fnd =
-                    faceToFaceID.find(face(sortedVerts));
+                const auto fnd = faceToFaceID.find(face(sortedVerts));
 
-                if (fnd != faceToFaceID.end())
+                if (fnd.found())
                 {
-                    label facei = fnd();
+                    label facei = *fnd;
                     int stat = face::compare(faces[i], boundaryFaces[facei]);
 
                     if (stat == 1)
diff --git a/applications/utilities/mesh/conversion/netgenNeutralToFoam/netgenNeutralToFoam.C b/applications/utilities/mesh/conversion/netgenNeutralToFoam/netgenNeutralToFoam.C
index 08c4b1e991..809f996afc 100644
--- a/applications/utilities/mesh/conversion/netgenNeutralToFoam/netgenNeutralToFoam.C
+++ b/applications/utilities/mesh/conversion/netgenNeutralToFoam/netgenNeutralToFoam.C
@@ -166,7 +166,7 @@ int main(int argc, char *argv[])
     label maxPatch = 0;
 
     // Boundary faces as three vertices
-    HashTable<label, triFace, Hash<triFace>> vertsToBoundary(nFaces);
+    HashTable<label, triFace, triFace::Hash<>> vertsToBoundary(nFaces);
 
     forAll(boundaryFaces, facei)
     {
@@ -215,12 +215,11 @@ int main(int argc, char *argv[])
 
             // Is there any boundary face with same vertices?
             // (uses commutative hash)
-            HashTable<label, triFace, Hash<triFace>>::iterator iter =
-                vertsToBoundary.find(triFace(f[0], f[1], f[2]));
+            auto iter = vertsToBoundary.find(triFace(f[0], f[1], f[2]));
 
-            if (iter != vertsToBoundary.end())
+            if (iter.found())
             {
-                label facei = iter();
+                label facei = iter.object();
                 const triFace& tri = iter.key();
 
                 // Determine orientation of tri v.s. cell centre.
diff --git a/src/OpenFOAM/containers/Lists/FixedList/FixedList.H b/src/OpenFOAM/containers/Lists/FixedList/FixedList.H
index bf954ce2bf..5d94034762 100644
--- a/src/OpenFOAM/containers/Lists/FixedList/FixedList.H
+++ b/src/OpenFOAM/containers/Lists/FixedList/FixedList.H
@@ -41,9 +41,10 @@ SourceFiles
 #include "label.H"
 #include "uLabel.H"
 #include "zero.H"
-#include "Hash.H"
+#include "contiguous.H"
 #include "autoPtr.H"
 #include "Swap.H"
+#include "HashFwd.H"
 #include "SLListFwd.H"
 
 #include <initializer_list>
@@ -137,19 +138,6 @@ public:
         typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
 
 
-    //- Hashing function class.
-    //  Use Hasher directly for contiguous data. Otherwise hash incrementally.
-    template<class HashT=Hash<T>>
-    struct Hash
-    {
-        inline unsigned operator()
-        (
-            const FixedList<T, Size>& list,
-            unsigned seed = 0
-        ) const;
-    };
-
-
     // Static Member Functions
 
         //- Return a null FixedList
@@ -438,10 +426,38 @@ public:
             Ostream& os,
             const FixedList<T, Size>& list
         );
+
+
+    // Hashing
+
+        //- Hashing function class for FixedList
+        //  Normally use the global Hash specialization, but can also use
+        //  this one for inheritance in sub-classes
+        template<class HashT=Foam::Hash<T>>
+        struct Hash
+        {
+            inline unsigned operator()
+            (
+                const FixedList<T, Size>& obj,
+                unsigned seed=0
+            ) const
+            {
+                if (contiguous<T>())
+                {
+                    return Hasher(obj.cdata(), Size*sizeof(T), seed);
+                }
+
+                for (const T& val : obj)
+                {
+                    seed = HashT()(val, seed);
+                }
+                return seed;
+            }
+        };
 };
 
 
-// Global Functions
+// * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * * //
 
 //- Swap FixedList contents - see FixedList::swap().
 //  Internally this actually swaps the individual list elements
@@ -449,6 +465,32 @@ template<class T, unsigned Size>
 inline void Swap(FixedList<T,Size>& lhs, FixedList<T,Size>& rhs);
 
 
+//- Hashing for FixedList data, which uses Hasher for contiguous data and
+//- element-wise incrementally hashing otherwise.
+template<>
+template<class T, unsigned N>
+struct Hash<FixedList<T, N>>
+{
+    inline unsigned operator()
+    (
+        const FixedList<T, N>& obj,
+        unsigned seed=0
+    ) const
+    {
+        if (contiguous<T>())
+        {
+            return Hasher(obj.cdata(), N*sizeof(T), seed);
+        }
+
+        for (const T& val : obj)
+        {
+            seed = Hash<T>()(val, seed);
+        }
+        return seed;
+    }
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam
diff --git a/src/OpenFOAM/containers/Lists/FixedList/FixedListI.H b/src/OpenFOAM/containers/Lists/FixedList/FixedListI.H
index ea687cda98..0945173818 100644
--- a/src/OpenFOAM/containers/Lists/FixedList/FixedListI.H
+++ b/src/OpenFOAM/containers/Lists/FixedList/FixedListI.H
@@ -25,8 +25,6 @@ License
 
 #include "UList.H"
 #include "SLList.H"
-#include "contiguous.H"
-
 #include <type_traits>
 #include <utility>
 
@@ -570,32 +568,6 @@ inline bool Foam::FixedList<T, Size>::empty() const
 }
 
 
-template<class T, unsigned Size>
-template<class HashT>
-inline unsigned Foam::FixedList<T, Size>::Hash<HashT>::operator()
-(
-    const FixedList<T, Size>& list,
-    unsigned seed
-) const
-{
-    if (contiguous<T>())
-    {
-        // Hash directly
-        return Hasher(list.v_, sizeof(list.v_), seed);
-    }
-
-    // Hash incrementally
-    unsigned val = seed;
-
-    for (unsigned i=0; i<Size; ++i)
-    {
-        val = HashT()(list[i], val);
-    }
-
-    return val;
-}
-
-
 // * * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * //
 
 template<class T, unsigned Size>
diff --git a/src/OpenFOAM/containers/Lists/List/List.H b/src/OpenFOAM/containers/Lists/List/List.H
index 151214cb56..93cab9f7b1 100644
--- a/src/OpenFOAM/containers/Lists/List/List.H
+++ b/src/OpenFOAM/containers/Lists/List/List.H
@@ -344,6 +344,30 @@ public:
 };
 
 
+// * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * * //
+
+//- Hashing for List data, which uses Hasher for contiguous data and
+//- element-wise incrementally hashing otherwise.
+template<>
+template<class T>
+struct Hash<List<T>>
+{
+    inline unsigned operator()(const UList<T>& obj, unsigned seed=0) const
+    {
+        if (contiguous<T>())
+        {
+            return Hasher(obj.cdata(), obj.size()*sizeof(T), seed);
+        }
+
+        for (const T& val : obj)
+        {
+            seed = Hash<T>()(val, seed);
+        }
+        return seed;
+    }
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam
diff --git a/src/OpenFOAM/containers/Lists/UList/UList.H b/src/OpenFOAM/containers/Lists/UList/UList.H
index 0ffa341f6a..246d566d9b 100644
--- a/src/OpenFOAM/containers/Lists/UList/UList.H
+++ b/src/OpenFOAM/containers/Lists/UList/UList.H
@@ -45,10 +45,12 @@ SourceFiles
 #include "bool.H"
 #include "label.H"
 #include "uLabel.H"
-#include "nullObject.H"
 #include "zero.H"
+#include "contiguous.H"
+#include "nullObject.H"
 #include "stdFoam.H"
 #include "Swap.H"
+#include "HashFwd.H"
 
 #include <initializer_list>
 #include <iterator>
@@ -529,10 +531,38 @@ public:
             }
             return false;
         }
+
+
+    // Other
+
+        //- Hashing function class for UList.
+        //  Can use this one (instead of the global Hash<>) for inheritance
+        //  in sub-classes
+        template<class HashT=Foam::Hash<T>>
+        struct Hash
+        {
+            inline unsigned operator()
+            (
+                const UList<T>& obj,
+                unsigned seed=0
+            ) const
+            {
+                if (contiguous<T>())
+                {
+                    return Hasher(obj.cdata(), obj.size()*sizeof(T), seed);
+                }
+
+                for (const T& val : obj)
+                {
+                    seed = HashT()(val, seed);
+                }
+                return seed;
+            }
+        };
 };
 
 
-// Global Functions
+// * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * * //
 
 template<class T>
 void sort(UList<T>& a);
@@ -562,6 +592,27 @@ template<class T>
 inline void Swap(UList<T>& a, UList<T>& b);
 
 
+//- Hashing for UList data, which uses Hasher for contiguous data and
+//- element-wise incrementally hashing otherwise.
+template<>
+template<class T>
+struct Hash<UList<T>>
+{
+    inline unsigned operator()(const UList<T>& obj, unsigned seed=0) const
+    {
+        if (contiguous<T>())
+        {
+            return Hasher(obj.cdata(), obj.size()*sizeof(T), seed);
+        }
+        for (const T& val : obj)
+        {
+            seed = Hash<T>()(val, seed);
+        }
+        return seed;
+    }
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam
diff --git a/src/OpenFOAM/containers/Lists/UList/UListI.H b/src/OpenFOAM/containers/Lists/UList/UListI.H
index 663d8d571d..76c8801305 100644
--- a/src/OpenFOAM/containers/Lists/UList/UListI.H
+++ b/src/OpenFOAM/containers/Lists/UList/UListI.H
@@ -24,6 +24,7 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "error.H"
+#include "contiguous.H"
 #include "pTraits.H"
 #include "Swap.H"
 
diff --git a/src/OpenFOAM/meshes/meshShapes/edge/edge.H b/src/OpenFOAM/meshes/meshShapes/edge/edge.H
index 6258fe8f98..81a6d1ef3a 100644
--- a/src/OpenFOAM/meshes/meshShapes/edge/edge.H
+++ b/src/OpenFOAM/meshes/meshShapes/edge/edge.H
@@ -95,7 +95,7 @@ public:
 
     // Member Functions
 
-      // Access
+    // Access
 
         //- Return first vertex label
         using labelPair::first;
@@ -124,7 +124,7 @@ public:
         inline edge reverseEdge() const;
 
 
-     // Queries
+    // Queries
 
         //- Return the smallest point label used by the edge
         //  No special handling of negative point labels.
@@ -155,7 +155,7 @@ public:
         inline label otherVertex(const label index) const;
 
 
-     // Editing
+    // Editing
 
         //- 'Collapse' edge by marking duplicate point labels as '-1',
         //  the lower vertex is retained.
@@ -163,7 +163,7 @@ public:
         inline label collapse();
 
 
-     // Hash-like functions
+    // Hash-like functions
 
         //- Return the number of unique, valid (non -1) point labels.
         //  Similar to a HashTable::size().
@@ -260,10 +260,43 @@ public:
         //  - -1: identical values, but in different order
         static inline int compare(const edge& a, const edge& b);
 
+
+    // Hashing
+
+        //- The (commutative) hash-value for edge
+        inline unsigned hashval(unsigned seed=0) const
+        {
+            if (first() < second())
+            {
+                seed = Foam::Hash<label>()(first(), seed);
+                seed = Foam::Hash<label>()(second(), seed);
+            }
+            else
+            {
+                seed = Foam::Hash<label>()(second(), seed);
+                seed = Foam::Hash<label>()(first(), seed);
+            }
+            return seed;
+        }
+
+        //- Hashing function class for edge (commutative)
+        //  Also useful for inheritance in sub-classes
+        template<class HashT=Foam::Hash<label>>
+        struct Hash
+        {
+            inline unsigned operator()(const edge& obj, unsigned seed=0) const
+            {
+                return obj.hashval(seed);
+            }
+        };
 };
 
 
-// * * * * * * * * * * * * * * Global Operators  * * * * * * * * * * * * * * //
+// * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * * //
+
+// Edges are a pair of labels - thus contiguous
+template<> inline bool contiguous<edge>()  {return true;}
+
 
 //- Return reverse of an edge
 inline edge reverse(const edge& e)
@@ -272,6 +305,19 @@ inline edge reverse(const edge& e)
 }
 
 
+//- Hash specialization for edge, using a commutative (incremental) hash.
+template<>
+struct Hash<edge>
+{
+    inline unsigned operator()(const edge& e, unsigned seed=0) const
+    {
+        return e.hashval(seed);
+    }
+};
+
+
+// * * * * * * * * * * * * * * Global Operators  * * * * * * * * * * * * * * //
+
 //- Compare edges for equal content, ignoring orientation
 inline bool operator==(const edge& a, const edge& b);
 
@@ -279,41 +325,6 @@ inline bool operator==(const edge& a, const edge& b);
 inline bool operator!=(const edge& a, const edge& b);
 
 
-//- Hash specialization for hashing edges as a commutative hash value.
-//  Hash incrementally.
-template<>
-inline unsigned Hash<edge>::operator()(const edge& e, unsigned seed) const
-{
-    unsigned val = seed;
-
-    if (e.first() < e.second())
-    {
-        val = Hash<label>()(e.first(), val);
-        val = Hash<label>()(e.second(), val);
-    }
-    else
-    {
-        val = Hash<label>()(e.second(), val);
-        val = Hash<label>()(e.first(), val);
-    }
-
-    return val;
-}
-
-
-//- Hash specialization for hashing edges as a commutative hash value.
-//  Hash incrementally.
-template<>
-inline unsigned Hash<edge>::operator()(const edge& e) const
-{
-    return Hash<edge>()(e, 0);
-}
-
-// Edges are a pair of labels - thus contiguous
-template<>
-inline bool contiguous<edge>()  {return true;}
-
-
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam
diff --git a/src/OpenFOAM/meshes/meshShapes/face/face.H b/src/OpenFOAM/meshes/meshShapes/face/face.H
index cedec1f73e..15aaa8e200 100644
--- a/src/OpenFOAM/meshes/meshShapes/face/face.H
+++ b/src/OpenFOAM/meshes/meshShapes/face/face.H
@@ -402,6 +402,19 @@ public:
 };
 
 
+// * * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * //
+
+//- Hash specialization for face
+template<>
+struct Hash<face>
+{
+    inline unsigned operator()(const face& obj, unsigned seed=0) const
+    {
+        return Hasher(obj.cdata(), obj.size()*sizeof(label), seed);
+    }
+};
+
+
 //- Specialization to offset faces, used in ListListOps::combineOffset
 template<>
 struct offsetOp<face>
@@ -414,27 +427,26 @@ struct offsetOp<face>
     {
         face result(x.size());
 
-        forAll(x, xI)
+        forAll(x, i)
         {
-            result[xI] = x[xI] + offset;
+            result[i] = x[i] + offset;
         }
         return result;
     }
 };
 
 
-// Global operators
-inline bool operator==(const face& a, const face& b);
-inline bool operator!=(const face& a, const face& b);
-
-
-// Global functions
-
 //- Find the longest edge on a face. Face point labels index into pts.
 //  \deprecated use class method instead (APR-2017)
 label longestEdge(const face& f, const UList<point>& pts);
 
 
+// * * * * * * * * * * * * * * * Global Operators  * * * * * * * * * * * * * //
+
+inline bool operator==(const face& a, const face& b);
+inline bool operator!=(const face& a, const face& b);
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam
diff --git a/src/OpenFOAM/meshes/meshShapes/triFace/triFace.H b/src/OpenFOAM/meshes/meshShapes/triFace/triFace.H
index 370a1079d8..aa6778ef6a 100644
--- a/src/OpenFOAM/meshes/meshShapes/triFace/triFace.H
+++ b/src/OpenFOAM/meshes/meshShapes/triFace/triFace.H
@@ -53,8 +53,7 @@ SourceFiles
 namespace Foam
 {
 
-// Forward declaration of friend functions and operators
-
+// Forward declarations
 class face;
 class triFace;
 
@@ -246,38 +245,52 @@ public:
         //  - -1: same face, but different orientation
         static inline int compare(const triFace& a, const triFace& b);
 
+
+    // Hashing
+
+        //- The (commutative) hash-value for triFace
+        inline unsigned hashval(unsigned seed=0) const
+        {
+            // Fortunately we don't need this very often
+            const uLabel t0((*this)[0]);
+            const uLabel t1((*this)[1]);
+            const uLabel t2((*this)[2]);
+
+            const uLabel val = (t0*t1*t2 + t0+t1+t2);
+
+            return Foam::Hash<uLabel>()(val, seed);
+        }
+
+        //- Hashing function class for triFace (commutative)
+        //  Also useful for inheritance in sub-classes
+        template<class HashT=Foam::Hash<label>>
+        struct Hash
+        {
+            inline unsigned operator()
+            (
+                const triFace& obj,
+                unsigned seed=0
+            ) const
+            {
+                return obj.hashval(seed);
+            }
+        };
 };
 
 
-template<>
-inline bool contiguous<triFace>()  {return true;}
-
-inline bool operator==(const triFace& a, const triFace& b);
-inline bool operator!=(const triFace& a, const triFace& b);
-
-
-//- Hash specialization for triFace as a commutative hash value.
-//  Hashes incrementally.
-template<>
-inline unsigned Hash<triFace>::operator()(const triFace& t, unsigned seed) const
-{
-    // Fortunately we don't need this very often
-    const uLabel t0(t[0]);
-    const uLabel t1(t[1]);
-    const uLabel t2(t[2]);
-
-    const uLabel val = (t0*t1*t2 + t0+t1+t2);
-
-    return Hash<uLabel>()(val, seed);
-}
+// * * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * //
 
+template<> inline bool contiguous<triFace>()  {return true;}
 
 //- Hash specialization for triFace as a commutative hash value.
 template<>
-inline unsigned Hash<triFace>::operator()(const triFace& t) const
+struct Hash<triFace>
 {
-    return Hash<triFace>::operator()(t, 0);
-}
+    inline unsigned operator()(const triFace& obj, unsigned seed=0) const
+    {
+        return obj.hashval(seed);
+    }
+};
 
 
 //- Specialization to offset faces, used in ListListOps::combineOffset
@@ -290,17 +303,23 @@ struct offsetOp<triFace>
         const label offset
     ) const
     {
-        triFace result(x);
+        triFace result;
 
-        forAll(x, xI)
+        forAll(x, i)
         {
-            result[xI] = x[xI] + offset;
+            result[i] = x[i] + offset;
         }
         return result;
     }
 };
 
 
+// * * * * * * * * * * * * * * * Global Operators  * * * * * * * * * * * * * //
+
+inline bool operator==(const triFace& a, const triFace& b);
+inline bool operator!=(const triFace& a, const triFace& b);
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam
diff --git a/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C b/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C
index 308496b555..c8e855f419 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C
@@ -200,11 +200,11 @@ int Foam::processorCyclicPolyPatch::tag() const
 
         if (owner())
         {
-            tag_ = Hash<word>()(cycPatch.name()) % 32768u;
+            tag_ = string::hash()(cycPatch.name()) % 32768u;
         }
         else
         {
-            tag_ = Hash<word>()(cycPatch.neighbPatch().name()) % 32768u;
+            tag_ = string::hash()(cycPatch.neighbPatch().name()) % 32768u;
         }
 
         if (tag_ == Pstream::msgType() || tag_ == -1)
diff --git a/src/OpenFOAM/primitives/Pair/Pair.H b/src/OpenFOAM/primitives/Pair/Pair.H
index 3209f4d942..af8d3a7321 100644
--- a/src/OpenFOAM/primitives/Pair/Pair.H
+++ b/src/OpenFOAM/primitives/Pair/Pair.H
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2017-2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -82,7 +82,7 @@ public:
 
     // Member Functions
 
-      // Access
+    // Access
 
         //- Return first element
         using FixedList<T, 2>::first;
@@ -100,13 +100,13 @@ public:
         inline const T& other(const T& a) const;
 
 
-     // Queries
+    // Queries
 
         //- True if first() is less-than second()
         inline bool sorted() const;
 
 
-     // Editing
+    // Editing
 
         //- Flip the Pair in-place.
         inline void flip();
@@ -115,7 +115,7 @@ public:
         inline void sort();
 
 
-     // Comparison
+    // Comparison
 
         //- Compare Pairs
         //  \return
@@ -123,6 +123,57 @@ public:
         //  - +1: identical values and order used
         //  - -1: identical values, but in reversed order
         static inline int compare(const Pair<T>& a, const Pair<T>& b);
+
+
+    // Hashing
+
+        //- Symmetrical hashing for Pair data.
+        //  The lower value is hashed first.
+        template<class HashT=Foam::Hash<T>>
+        struct SymmHash
+        {
+            inline unsigned operator()
+            (
+                const Pair<T>& obj,
+                unsigned seed=0
+            ) const
+            {
+                if (obj.first() < obj.second())
+                {
+                    seed = HashT()(obj.first(), seed);
+                    seed = HashT()(obj.second(), seed);
+                }
+                else
+                {
+                    seed = HashT()(obj.second(), seed);
+                    seed = HashT()(obj.first(), seed);
+                }
+                return seed;
+            }
+        };
+};
+
+
+// * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * * //
+
+//- Hashing for Pair data, which uses Hasher for contiguous data and
+//- element-wise incrementally hashing otherwise.
+template<>
+template<class T>
+struct Hash<Pair<T>>
+{
+    inline unsigned operator()(const Pair<T>& obj, unsigned seed=0) const
+    {
+        if (contiguous<T>())
+        {
+            return Hasher(obj.cdata(), sizeof(obj), seed);
+        }
+
+        seed = Hash<T>()(obj.first(), seed);
+        seed = Hash<T>()(obj.second(), seed);
+
+        return seed;
+    }
 };
 
 
diff --git a/src/OpenFOAM/primitives/hashes/Hash/Hash.H b/src/OpenFOAM/primitives/hashes/Hash/Hash.H
index 1ec3fc5af2..38fe567708 100644
--- a/src/OpenFOAM/primitives/hashes/Hash/Hash.H
+++ b/src/OpenFOAM/primitives/hashes/Hash/Hash.H
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2012 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -25,7 +25,8 @@ Class
     Foam::Hash
 
 Description
-    Hash function class for primitives.  All non-primitives used to hash
+    Hash function class.
+    The default definition is for primitives, non-primitives used to hash
     entries on hash tables likely need a specialized version of this class.
 
 \*---------------------------------------------------------------------------*/
@@ -36,7 +37,6 @@ Description
 #include "label.H"
 #include "uLabel.H"
 #include "Hasher.H"
-#include "pTraits.H"
 #include "fileName.H"
 #include "wordRe.H"
 
@@ -44,8 +44,6 @@ Description
 
 namespace Foam
 {
-//template<class Type> struct Hash;
-//template<> struct Hash<label>;
 
 /*---------------------------------------------------------------------------*\
                             Class Hash Declaration
@@ -54,134 +52,106 @@ namespace Foam
 template<class PrimitiveType>
 struct Hash
 {
-    unsigned operator()(const PrimitiveType& p, unsigned seed) const
+    inline unsigned operator()(const PrimitiveType& obj, unsigned seed=0) const
     {
-        return Hasher(&p, sizeof(p), seed);
+        return Hasher(&obj, sizeof(obj), seed);
     }
-
-    unsigned operator()(const PrimitiveType& p) const
-    {
-        return Hasher(&p, sizeof(p));
-    }
-
 };
 
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-//- Hash specialization for hashing labels
+//- Hash specialization for label
 template<>
 struct Hash<Foam::label>
 {
     //- Incrementally hash a label.
     //  This will necessarily return a different value than the
     //  non-incremental version.
-    unsigned operator()(const label p, unsigned seed) const
+    inline unsigned operator()(const label obj, unsigned seed) const
     {
-        return Hasher(&p, sizeof(label), seed);
+        return Hasher(&obj, sizeof(label), seed);
     }
 
     //- Return the unsigned representation of a label.
     //  This helps if people have relied on the hash value corresponding to
     //  the natural order.
-    unsigned operator()(const label p) const
+    inline unsigned operator()(const label obj) const
     {
-        return p;
+        return obj;
     }
 };
 
 
-//- Hash specialization for hashing strings
+//- Hash specialization for string
 template<>
 struct Hash<Foam::string>
 {
-    unsigned operator()(const string& p, unsigned seed) const
+    inline unsigned operator()(const string& obj, unsigned seed=0) const
     {
-        return string::hash()(p, seed);
-    }
-    unsigned operator()(const string& p) const
-    {
-        return string::hash()(p);
+        return string::hash()(obj, seed);
     }
 };
 
 
-//- Hash specialization for hashing words
+//- Hash specialization for word
 template<>
 struct Hash<Foam::word>
 {
-    unsigned operator()(const word& p, unsigned seed) const
+    inline unsigned operator()(const word& obj, unsigned seed=0) const
     {
-        return word::hash()(p, seed);
-    }
-    unsigned operator()(const word& p) const
-    {
-        return word::hash()(p);
+        return string::hash()(obj, seed);
     }
 };
 
 
-//- Hash specialization for hashing fileNames
+//- Hash specialization for fileName
 template<>
 struct Hash<Foam::fileName>
 {
-    unsigned operator()(const fileName& p, unsigned seed) const
+    inline unsigned operator()(const fileName& obj, unsigned seed=0) const
     {
-        return fileName::hash()(p, seed);
-    }
-    unsigned operator()(const fileName& p) const
-    {
-        return fileName::hash()(p);
+        return string::hash()(obj, seed);
     }
 };
 
 
-//- Hash specialization for hashing wordRes
+//- Hash specialization for wordRe
 template<>
 struct Hash<Foam::wordRe>
 {
-    unsigned operator()(const wordRe& p, unsigned seed) const
+    inline unsigned operator()(const wordRe& obj, unsigned seed=0) const
     {
-        return wordRe::hash()(p, seed);
-    }
-    unsigned operator()(const wordRe& p) const
-    {
-        return wordRe::hash()(p);
+        return string::hash()(obj, seed);
     }
 };
 
 
-//- Hash specialization for hashing keyTypes
+//- Hash specialization for keyType
 template<>
 struct Hash<Foam::keyType>
 {
-    unsigned operator()(const keyType& p, unsigned seed) const
+    inline unsigned operator()(const keyType& obj, unsigned seed=0) const
     {
-        return keyType::hash()(p, seed);
-    }
-    unsigned operator()(const keyType& p) const
-    {
-        return keyType::hash()(p);
+        return string::hash()(obj, seed);
     }
 };
 
 
-//- Hash specialization for hashing pointer addresses.
-//  Treat a pointer like a long.
-//  This should work for both 32-bit and 64-bit pointers.
+//- Hash specialization for pointers.
+//  Interpret pointer as a long (works for 32-bit and 64-bit pointers).
 template<>
 struct Hash<void*>
 {
-    unsigned operator()(const void* const& p, unsigned seed) const
+    inline unsigned operator()(const void* const& obj, unsigned seed) const
     {
-        return Hash<long>()(long(p), seed);
+        return Hash<long>()(long(obj), seed);
     }
 
-    unsigned operator()(const void* const& p) const
+    inline unsigned operator()(const void* const& obj) const
     {
-        return Hash<long>()(long(p));
+        return Hash<long>()(long(obj));
     }
-
 };
 
 
diff --git a/src/OpenFOAM/primitives/hashes/Hash/HashFwd.H b/src/OpenFOAM/primitives/hashes/Hash/HashFwd.H
new file mode 100644
index 0000000000..010ca3d2be
--- /dev/null
+++ b/src/OpenFOAM/primitives/hashes/Hash/HashFwd.H
@@ -0,0 +1,46 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2018 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Description
+    Forward definition for Hash function class and the definition for
+    the Hasher function.
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef HashFwd_H
+#define HashFwd_H
+
+#include "Hasher.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+    template<class T> struct Hash;
+}
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/primitives/hashes/Hasher/Hasher.H b/src/OpenFOAM/primitives/hashes/Hasher/Hasher.H
index 7fcb086ec4..948d4bd49d 100644
--- a/src/OpenFOAM/primitives/hashes/Hasher/Hasher.H
+++ b/src/OpenFOAM/primitives/hashes/Hasher/Hasher.H
@@ -53,11 +53,21 @@ namespace Foam
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-    //- Bob Jenkins's 96-bit mixer hashing function (lookup3)
-    //  \param[in] data - a character stream
-    //  \param[in] len  - the number of bytes
-    //  \param[in] seed - the previous hash, or an arbitrary value
-    unsigned Hasher(const void* data, size_t len, unsigned seed = 0);
+//- Bob Jenkins's 96-bit mixer hashing function (lookup3)
+//  \param[in] data - a character stream
+//  \param[in] len  - the number of bytes
+//  \param[in] seed - the previous hash, or an arbitrary value
+unsigned Hasher(const void* data, size_t len, unsigned seed = 0);
+
+
+//- Hashing of bit-wise internal content of given data object.
+//  For primitives and simple collections of primitives this is reasonable,
+//  but ill-advised for more complex data structures.
+template<class T>
+inline unsigned HasherT(const T& obj, unsigned seed = 0)
+{
+    return Hasher(&obj, sizeof(obj), seed);
+}
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
diff --git a/src/sampling/surface/cuttingPlane/cuttingPlane.C b/src/sampling/surface/cuttingPlane/cuttingPlane.C
index 9838cd7323..051a60c1cb 100644
--- a/src/sampling/surface/cuttingPlane/cuttingPlane.C
+++ b/src/sampling/surface/cuttingPlane/cuttingPlane.C
@@ -26,9 +26,8 @@ License
 #include "cuttingPlane.H"
 #include "fvMesh.H"
 #include "volFields.H"
-#include "linePointRef.H"
 #include "meshTools.H"
-#include "EdgeMap.H"
+#include "edgeHashes.H"
 #include "HashOps.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
@@ -80,29 +79,8 @@ namespace Foam
     }
 
 
-    //- Hash specialization for labelList. Hash incrementally.
-    template<>
-    inline unsigned Hash<labelList>::operator()
-    (
-        const labelList& list,
-        unsigned seed
-    ) const
-    {
-        return Hasher(list.cdata(), list.size()*sizeof(label), seed);
-    }
-
-    //- Hash specialization for labelList
-    template<>
-    inline unsigned Hash<labelList>::operator()
-    (
-        const labelList& list
-    ) const
-    {
-        return Hash<labelList>()(list, 0);
-    }
-
     //- For hashing face point labels, which are pre-sorted.
-    typedef HashSet<labelList, Hash<labelList>> labelListHashSet;
+    typedef HashSet<labelList, labelList::Hash<>> labelListHashSet;
 
 } // End namespace Foam
 
@@ -354,6 +332,7 @@ void Foam::cuttingPlane::walkCellCuts
             {
                 edge e(f.faceEdge(fp));
 
+                // Action #1: detect edge intersection and orient edge
                 if (!intersectEdgeOrient(sides, e))
                 {
                     continue;
@@ -388,6 +367,7 @@ void Foam::cuttingPlane::walkCellCuts
                 const point& p0 = points[e[0]];
                 const point& p1 = points[e[1]];
 
+                // Action #2: edge cut alpha
                 const scalar alpha =
                     this->lineIntersect(linePointRef(p0, p1));
 
@@ -540,6 +520,7 @@ void Foam::cuttingPlane::walkCellCuts
 
         face f(localFaceLoop);
 
+        // Action #3: orient face
         // Orient face to point in the same direction as the plane normal
         if ((f.areaNormal(dynCutPoints) & this->normal()) < 0)
         {
diff --git a/src/surfMesh/surfaceFormats/obj/OBJstream.H b/src/surfMesh/surfaceFormats/obj/OBJstream.H
index c19310938a..3bc39b3809 100644
--- a/src/surfMesh/surfaceFormats/obj/OBJstream.H
+++ b/src/surfMesh/surfaceFormats/obj/OBJstream.H
@@ -40,7 +40,6 @@ SourceFiles
 #include "edge.H"
 #include "face.H"
 #include "triPointRef.H"
-#include "linePointRef.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //