diff --git a/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C b/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C
index 93277a1ea5..72cd0a30e4 100644
--- a/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C
+++ b/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C
@@ -242,6 +242,63 @@ Foam::lduPrimitiveMesh::lduPrimitiveMesh
 }
 
 
+//Foam::lduPrimitiveMesh::lduPrimitiveMesh
+//(
+//    const label nCells,
+//    labelList& l,
+//    labelList& u,
+//    labelListList& pa,
+//    PtrList<const lduInterface>& primitiveInterfaces,
+//    const lduSchedule& ps,
+//    const label comm,
+//    bool reUse
+//)
+//:
+//    lduAddressing(nCells),
+//    lowerAddr_(l, reUse),
+//    upperAddr_(u, reUse),
+//    patchAddr_(pa, reUse),
+//    primitiveInterfaces_(primitiveInterfaces, reUse),
+//    patchSchedule_(ps),
+//    comm_(comm)
+//{
+//    interfaces_.setSize(primitiveInterfaces_.size());
+//    forAll(primitiveInterfaces, intI)
+//    {
+//        interfaces_.set(intI, &primitiveInterfaces_[intI]);
+//    }
+//
+//    //Pout<< "lduPrimitiveMesh :"
+//    //    << " nCells:" << nCells
+//    //    << " l:" << lowerAddr_.size()
+//    //    << " u:" << upperAddr_.size()
+//    //    << " pa:" << patchAddr_.size()
+//    //    << " interfaces:" << interfaces_.size()
+//    //    << " comm:" << comm_
+//    //    << endl;
+//    //forAll(interfaces_, i)
+//    //{
+//    //    if (interfaces_.set(i))
+//    //    {
+//    //        if (isA<processorLduInterface>(interfaces_[i]))
+//    //        {
+//    //            const processorLduInterface& pi = refCast
+//    //            <
+//    //                const processorLduInterface
+//    //            >(interfaces_[i]);
+//    //
+//    //            Pout<< "    patch:" << i
+//    //                << " size:" << patchAddr_[i].size()
+//    //                << " myProcNo:" << pi.myProcNo()
+//    //                << " neighbProcNo:" << pi.neighbProcNo()
+//    //                << " comm:" << pi.comm()
+//    //                << endl;
+//    //        }
+//    //    }
+//    //}
+//}
+
+
 Foam::lduPrimitiveMesh::lduPrimitiveMesh
 (
     const label comm,
@@ -252,6 +309,7 @@ Foam::lduPrimitiveMesh::lduPrimitiveMesh
     const PtrList<lduMesh>& otherMeshes,
 
     labelList& cellOffsets,
+    labelList& faceOffsets,
     labelListList& faceMap,
     labelListList& boundaryMap,
     labelListListList& boundaryFaceMap
@@ -271,14 +329,14 @@ Foam::lduPrimitiveMesh::lduPrimitiveMesh
     {
         if (otherMeshes[i].comm() != currentComm)
         {
-            FatalErrorIn
+            WarningIn
             (
                 "lduPrimitiveMesh::lduPrimitiveMesh(..)"
             )   << "Communicator " << otherMeshes[i].comm()
                 << " at index " << i
                 << " differs from that of predecessor "
                 << currentComm
-                << exit(FatalError);
+                << endl;    //exit(FatalError);
         }
     }
 
@@ -527,7 +585,7 @@ Foam::lduPrimitiveMesh::lduPrimitiveMesh
 
 
     // Adapt faceOffsets for internal interfaces
-    labelList faceOffsets(nMeshes+1);
+    faceOffsets.setSize(nMeshes+1);
     faceOffsets[0] = 0;
     faceMap.setSize(nMeshes);
     for (label procMeshI = 0; procMeshI < nMeshes; procMeshI++)
@@ -836,6 +894,7 @@ const Foam::lduMesh& Foam::lduPrimitiveMesh::mesh
 
 void Foam::lduPrimitiveMesh::gather
 (
+    const label comm,
     const lduMesh& mesh,
     const labelList& procIDs,
     PtrList<lduMesh>& otherMeshes
@@ -844,10 +903,7 @@ void Foam::lduPrimitiveMesh::gather
     // Force calculation of schedule (since does parallel comms)
     (void)mesh.lduAddr().patchSchedule();
 
-
-    const label meshComm = mesh.comm();
-
-    if (Pstream::myProcNo(meshComm) == procIDs[0])
+    if (Pstream::myProcNo(comm) == procIDs[0])
     {
         otherMeshes.setSize(procIDs.size()-1);
 
@@ -863,7 +919,7 @@ void Foam::lduPrimitiveMesh::gather
                 procIDs[i],
                 0,          // bufSize
                 Pstream::msgType(),
-                meshComm
+                comm
             );
 
             label nCells = readLabel(fromSlave);
@@ -909,13 +965,13 @@ void Foam::lduPrimitiveMesh::gather
                     (
                         newInterfaces
                     ),
-                    meshComm,
+                    comm,
                     true
                 )
             );
         }
     }
-    else if (findIndex(procIDs, Pstream::myProcNo(meshComm)) != -1)
+    else if (findIndex(procIDs, Pstream::myProcNo(comm)) != -1)
     {
         // Send to master
 
@@ -933,7 +989,7 @@ void Foam::lduPrimitiveMesh::gather
             procIDs[0],
             0,
             Pstream::msgType(),
-            meshComm
+            comm
         );
 
         //Pout<< "sent nCells:" << addressing.size()
diff --git a/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.H b/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.H
index 30e44923ad..1bd01e9fa6 100644
--- a/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.H
+++ b/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.H
@@ -68,7 +68,7 @@ class lduPrimitiveMesh
         lduInterfacePtrsList interfaces_;
 
         //- Concrete interfaces if above interfaces were created locally
-        PtrList<lduInterface> primitiveInterfaces_;
+        PtrList<const lduInterface> primitiveInterfaces_;
 
         //- Patch field evaluation schedule
         lduSchedule patchSchedule_;
@@ -139,16 +139,28 @@ public:
         //                  similar to cell-restrict-addressing.
         //                  We need this information to be able to map
         //                  inter-processor interfaces
+        // cellOffsets : for every processor the offset it gets in the mesh
+        // faceMap     : for every processor, for every face, the destination
+        //               face. Negative for flipped faces.
+        // boundaryMap : for every processor, for every patch, -1 or the new
+        //               patch index in the mesh.
+        // boundaryFaceMap : for every processor, for every patch, for every
+        //                   patch face:
+        //                   - the new internal face (if boundaryMap=-1)
+        //                   - the new patch face (if boundaryMap>=0)
+        //                   Faces becoming internal are negative for flipped
+        //                   faces.
         lduPrimitiveMesh
         (
             const label comm,
             const labelList& procAgglomMap,
 
-            const labelList& procIDs,               // procIDs[0] = myMesh
+            const labelList& procIDs,
             const lduMesh& myMesh,
             const PtrList<lduMesh>& otherMeshes,
 
             labelList& cellOffsets,
+            labelList& faceOffsets,
             labelListList& faceMap,
             labelListList& boundaryMap,
             labelListListList& boundaryFaceMap
@@ -177,6 +189,14 @@ public:
                 return interfaces_;
             }
 
+            //- Return a list of pointers for each patch
+            //  with only those pointing to interfaces being set
+            //  (reference to cached interfaces)
+            const lduInterfacePtrsList& rawInterfaces() const
+            {
+                return interfaces_;
+            }
+
             //- Return communicator used for parallel communication
             virtual label comm() const
             {
@@ -219,9 +239,10 @@ public:
             );
 
             //- Gather meshes from other processors onto procIDs[0].
-            //  Hardcoded for GAMGInterface.
+            //  Received meshes get GAMGInterface and communicator comm
             static void gather
             (
+                const label comm,
                 const lduMesh& mesh,
                 const labelList& procIDs,
                 PtrList<lduMesh>& otherMeshes