Add communication when multiplying with the matrix duneB_ in apply

Here we go from cells to segments, and everything concerning segments is stored globally.

opm/simulators/wells/MultisegmentWellEquations.cpp

@@ -152,6 +152,11 @@ apply(const BVector& x, BVector& Ax) const
 
     duneB_.mv(x, Bx);
 
+    if (this->pw_info_.communication().size() == 1) {
+        // We need to communicate here to get the contributions from all segments
+        this->pw_info_.communication().sum(Bx.data(), Bx.size());
+    }
+
     // invDBx = duneD^-1 * Bx_
     const BVectorWell invDBx = mswellhelpers::applyUMFPack(*duneDSolver_, Bx);