feat(poly): preconditioner is now being computed

src/poly/solver/public/polySolver.h

@@ -19,6 +19,12 @@ namespace laneEmden {
     double thetaSeriesExpansion(double xi, double n, int order);
 }
 
+// Struct to persist lifetime of the linear and nonlinear solvers
+struct solverBundle {
+    mfem::GMRESSolver solver;
+    mfem::NewtonSolver newton;
+};
+
 class PolySolver {
 public: // Public methods
     PolySolver(double n, double order);
@@ -58,7 +64,7 @@ private: // Private methods
     std::pair<mfem::Array<int>, mfem::Array<int>> findCenterElement() const;
     void setInitialGuess() const;
     void saveAndViewSolution(const mfem::BlockVector& state_vector) const;
-    mfem::NewtonSolver setupNewtonSolver() const;
+    solverBundle setupNewtonSolver() const;
     void setupOperator() const;
 
     void LoadSolverUserParams(double &newtonRelTol, double &newtonAbsTol, int &newtonMaxIter, int &newtonPrintLevel,