changed start of using extrapolation

src/elasticity/solvers/IterativePressureSolver.cpp

@@ -33,7 +33,7 @@ bool IterativePressureSolver::Method(IElasticity &assemble, Vector &u) {
   while (!iteration.IsFinished()) {
     int n = iteration.Step();
 
-    if (n > 1) {
+    if (n > 0) {
       uOld = uNew;  // u^{n-1}
     }
 
@@ -55,8 +55,8 @@ bool IterativePressureSolver::Method(IElasticity &assemble, Vector &u) {
         return Method(assemble, u);
       return false;
     }
-    // Extrapolation ab n = 2
-    if (useExtrapolation && n >= 2) {
+    // Extrapolation ab n = 1
+    if (useExtrapolation && n >= 1) {
       deltaU = uNew - uOld;
       uNew += dampingExtrapolation * deltaU;
     }