improving start residuum for next pressure iteration and removed u.Clear() in CalculatePrestress

src/elasticity/solvers/IterativePressureSolver.cpp

@@ -23,8 +23,13 @@ bool IterativePressureSolver::Method(IElasticity &assemble, Vector &u) {
   Vector uNew(u);
 
   Initialize(assemble, uNew);
+  Vector d(uNew);
+  d = 0;
   while (!iteration.IsFinished()) {
+    Vector uOld(uNew);
+    uNew += d;
     bool converged = Step(assemble, uNew);
+    d = uNew - uOld;
     if(converged) {
       assemble.PrintPressureIteration(uNew);
       assemble.PlotPressureIteration(uNew, iteration.Step());
@@ -87,5 +92,5 @@ void CalculatePrestress(IElasticity &assemble, Vector &u) {
   IterativePressureSolver prestressSolver(assemble.GetElasticityProblem(), prestressSteps);
   prestressSolver.Method(assemble, u);
   assemble.InitializePrestress(u);
-  u.Clear();
+  //u.Clear();
 }