[PL] GW: Add MeshSubsets and MeshComponentMap.

ProcessLib/GroundwaterFlowProcess.h

@@ -14,6 +14,8 @@
 #include "logog/include/logog.hpp"
 
 #include "MeshLib/Mesh.h"
+#include "MeshLib/MeshSubset.h"
+#include "MeshLib/MeshSubsets.h"
 #include "ProcessVariable.h"
 
 namespace ProcessLib
@@ -51,14 +53,28 @@ public:
 
     void initialize()
     {
+        // Create mesh's subset using all nodes of the mesh.
+        _mesh_subset_all_nodes = new MeshLib::MeshSubset(_mesh, _mesh.getNodes());
+
+        // Define a mesh item composition in a vector.
+        _all_mesh_subsets.push_back(new MeshLib::MeshSubsets(_mesh_subset_all_nodes));
+        AssemblerLib::MeshComponentMap mesh_component_map(_all_mesh_subsets,
+                AssemblerLib::ComponentOrder::BY_COMPONENT);
     }
 
     ~GroundwaterFlowProcess()
     {
+        for (auto p : _all_mesh_subsets)
+            delete p;
+
+        delete _mesh_subset_all_nodes;
     }
 
 private:
     ProcessVariable const* _hydraulic_head = nullptr;
+
+    MeshLib::MeshSubset const* _mesh_subset_all_nodes = nullptr;
+    std::vector<MeshLib::MeshSubsets*> _all_mesh_subsets;
 };
 
 }   // namespace ProcessLib