add a factorization before using the inner(Cholmod)solver of...

add a factorization before using the inner(Cholmod)solver of RiemannianpnSolver to catch matrices that are not positive definit.

dune/gfe/riemannianpnsolver.cc

@@ -329,9 +329,14 @@ void Dune::GFE::RiemannianProximalNewtonSolver<Basis,TargetSpace,Assembler>::sol
 
       Dune::Timer solutionTimer;
       try {
+        //factorize matrix beforehand to check if positive definite beforehand.
+        innerSolver_->factorize();
+        if(innerSolver_->errorCode() == 1 )
+          DUNE_THROW(Dune::MathError, "Matrix used for CHOLMOD not positive definite!");
+
         innerSolver_->solve();
-      } catch (Dune::Exception &e) {
-        std::cerr << "Error while solving: " << e << std::endl;
+      } catch ( ... ) {
+        std::cerr << "Error while solving: " << std::endl;
         solved = false;
         corr_global = 0;
       }