function for accumulative efficiency factor for WellNode

This is the final efficiency factor that goes to the source/sink terms
in the material balance equations.

opm/core/wells/WellsGroup.cpp

@@ -1295,7 +1295,9 @@ namespace Opm
             production_specification.reservoir_flow_max_rate_ = group.getReservoirVolumeTargetRate(timeStep);
         }
 
-        std::shared_ptr<WellsGroupInterface> wells_group(new WellsGroup(group.name(), production_specification, injection_specification, phase_usage));
+        const double efficiency_factor = group.getGroupEfficiencyFactor(timeStep);
+
+        std::shared_ptr<WellsGroupInterface> wells_group(new WellsGroup(group.name(), efficiency_factor, production_specification, injection_specification, phase_usage));
         return wells_group;
     }
 
@@ -1339,4 +1341,21 @@ namespace Opm
         std::shared_ptr<WellsGroupInterface> wells_group(new WellNode(well->name(), efficiency_factor, production_specification, injection_specification, phase_usage));
         return wells_group;
     }
+
+
+
+
+    double WellNode::getAccumulativeEfficiencyFactor() const {
+        // TODO: not sure whether a well can be exempted from repsponding to the efficiency factor
+        // for the parent group.
+        double efficicency_factor = efficicencyFactor();
+        const WellsGroupInterface* parent_node = getParent();
+        while (parent_node != nullptr) {
+            efficicency_factor *= parent_node->efficicencyFactor();
+            parent_node = parent_node->getParent();
+        }
+
+        return efficicency_factor;
+    }
+
 }

opm/core/wells/WellsGroup.hpp

@@ -233,6 +233,9 @@ namespace Opm
 
         virtual void updateWellInjectionTargets(const std::vector<double>& well_rates) = 0;
 
+        double efficicencyFactor() const;
+
+        void setEfficiencyFactor(const double efficicency_factor);
 
     protected:
         /// Calculates the correct rate for the given ProductionSpecification::ControlMode
@@ -245,9 +248,6 @@ namespace Opm
                           const double* surf_rates,
                           const InjectionSpecification::ControlMode mode);
 
-        double efficicencyFactor() const;
-        void setEfficiencyFactor(const double efficicency_factor);
-
         WellsGroupInterface* parent_;
 
         // when some well (mabye group also later), change status from group control
@@ -469,6 +469,9 @@ namespace Opm
 
         virtual void updateWellInjectionTargets(const std::vector<double>& well_rates);
 
+        /// the efficiency factor for groups are muliplitive, this function return the resulted final efficiency factor
+        /// to the well in a multi-layer group structure.
+        double getAccumulativeEfficiencyFactor() const;
 
     private:
         Wells* wells_;