Directly compute the iteration radius when no preconditioner is given

[[Imported from SVN: r2452]]

dune-solvers/solvers/tcgsolver.cc

@@ -108,6 +108,22 @@ void TruncatedCGSolver<MatrixType, VectorType>::solve()
                   << std::endl;
 #endif
 
+        if (preconditioner_==NULL) {
+
+            correctionNormSquared = trustRegionScalarProduct(p,p);
+            solutionTimesCorrection = trustRegionScalarProduct(*x_,p);
+            solutionNormSquared = trustRegionScalarProduct(*x_,*x_);
+
+        }
+
+        if (correctionNormSquared <= 0) {
+            
+            if (this->historyBuffer_!="")
+                this->writeIterate(*x_, i);
+            return;
+
+        }
+
         // if energy is concave in the search direction go to the boundary and stop there
         if (energyNormSquared <= 0) {
 
@@ -146,7 +162,7 @@ void TruncatedCGSolver<MatrixType, VectorType>::solve()
 
 //         std::cout << "tentative radius^2: " << trustRegionScalarProduct(tentativeNewIterate,tentativeNewIterate)
 //                   << std::endl;
-        std::cout << "tentative length^2: " << tentativeLengthSquared << std::endl;
+        //std::cout << "tentative length^2: " << tentativeLengthSquared << std::endl;
 
         if (tentativeLengthSquared >= trustRegionRadius_*trustRegionRadius_) {