Revert "fix a bug in linear solver creation. it should be created after assemlying A."

This reverts commit 0237275a.

ProcessLib/GroundwaterFlowProcess.h

@@ -215,6 +215,8 @@ public:
         _A.reset(_global_setup.createMatrix(_local_to_global_index_map->dofSize()));
         _x.reset(_global_setup.createVector(_local_to_global_index_map->dofSize()));
         _rhs.reset(_global_setup.createVector(_local_to_global_index_map->dofSize()));
+        _linearSolver.reset(new typename GlobalSetup::LinearSolver(*_A));
+
 
         setInitialConditions(*_hydraulic_head);
 
@@ -261,8 +263,7 @@ public:
         // Apply known values from the Dirichlet boundary conditions.
         MathLib::applyKnownSolution(*_A, *_rhs, _dirichlet_bc.global_ids, _dirichlet_bc.values);
 
-        typename GlobalSetup::LinearSolver linearSolver(*_A);
-        linearSolver.solve(*_rhs, *_x);
+        _linearSolver->solve(*_rhs, *_x);
 
         return true;
     }
@@ -325,6 +326,7 @@ private:
     std::vector<MeshLib::MeshSubsets*> _all_mesh_subsets;
 
     GlobalSetup _global_setup;
+    std::unique_ptr<typename GlobalSetup::LinearSolver> _linearSolver;
     std::unique_ptr<typename GlobalSetup::MatrixType> _A;
     std::unique_ptr<typename GlobalSetup::VectorType> _rhs;
     std::unique_ptr<typename GlobalSetup::VectorType> _x;