Fix master-group potential double conversion

A reservoir-coupling master group takes its production potential from
the corresponding slave group, which reports it in display units (e.g.
SM3/DAY for METRIC): the slave applies from_si before storing the value
in its GroupState and sending it to the master. The guide-rate handler
then applied from_si a second time to that value, inflating a master
group's potential by the seconds-per-day factor (86400 in METRIC).

This does not change the physical solution when every producing group
under a parent is a master group, because the GUIDERAT denominator is
built from rate ratios, so a uniform scaling of all potentials cancels
in the guide-rate fractions. But it corrupts the reported group
production guide rates (GOPGR/GVPGR) and would distort the split in a
mixed hierarchy of master and ordinary producing groups.

Apply from_si only to non-master groups, whose potentials are
accumulated from sub-groups in SI; a master group's potential is
already in display units and must not be converted again.

opm/simulators/wells/GuideRateHandler.cpp

@@ -444,21 +444,6 @@ update()
 // Inner class UpdateGuideRates private methods sorted alphabetically
 // --------------------------------------------------------------------
 
-#ifdef RESERVOIR_COUPLING_ENABLED
-template<typename Scalar, typename IndexTraits>
-bool
-GuideRateHandler<Scalar, IndexTraits>::UpdateGuideRates::
-isMasterGroup_(const Group& group)
-{
-    if (this->isReservoirCouplingMaster()) {
-        return this->reservoirCouplingMaster().isMasterGroup(group.name());
-    }
-    else {
-        return false;
-    }
-}
-#endif
-
 template<typename Scalar, typename IndexTraits>
 void
 GuideRateHandler<Scalar, IndexTraits>::UpdateGuideRates::
@@ -564,8 +549,9 @@ updateGuideRatesForProductionGroups_(const Group& group, std::vector<Scalar>& po
     // NOTE: Even if this is a pure injection group, we still need to compute the
     // group potentials since they may be used by a production group at a higher
     // level in the group hierarchy. See MOD4_UDQ_ACTIONX.DATA for an example.
+    const bool is_master_group = this->isMasterGroup_(group);
 #ifdef RESERVOIR_COUPLING_ENABLED
-    if (this->isMasterGroup_(group)) {
+    if (is_master_group) {
         // This is a master group, so we do not need to compute potentials
         // for sub groups. We just set the guide rates for the master group
         // as submitted from its corresponding slave group.
@@ -595,9 +581,17 @@ updateGuideRatesForProductionGroups_(const Group& group, std::vector<Scalar>& po
 
     // Synchronize potentials across all ranks
     this->comm().sum(potentials.data(), potentials.size());
-    oil_pot = this->unit_system_.from_si(UnitSystem::measure::liquid_surface_rate, oil_pot);
-    water_pot = this->unit_system_.from_si(UnitSystem::measure::liquid_surface_rate, water_pot);
-    gas_pot = this->unit_system_.from_si(UnitSystem::measure::gas_surface_rate, gas_pot);
+    if (!is_master_group) {
+        // Non-master group potentials are accumulated from sub-groups in SI;
+        // convert them to the display units (e.g. SM3/DAY for METRIC) that
+        // GuideRate::compute() and the stored group potential use. A master
+        // group's potential already arrives in display units from its slave
+        // group (the slave applied from_si before storing and sending it), so
+        // it must not be converted again here.
+        oil_pot = this->unit_system_.from_si(UnitSystem::measure::liquid_surface_rate, oil_pot);
+        water_pot = this->unit_system_.from_si(UnitSystem::measure::liquid_surface_rate, water_pot);
+        gas_pot = this->unit_system_.from_si(UnitSystem::measure::gas_surface_rate, gas_pot);
+    }
     this->guideRate().compute(
         group.name(), this->report_step_idx_, this->sim_time_, oil_pot, gas_pot, water_pot
     );

opm/simulators/wells/GuideRateHandler.hpp

@@ -134,9 +134,9 @@ public:
         void update();
 
     private:
-#ifdef RESERVOIR_COUPLING_ENABLED
-        bool isMasterGroup_(const Group& group);
-#endif
+        bool isMasterGroup_(const Group& group) const {
+            return this->parent_.rescoup().isMasterGroup(group.name());
+        }
         void updateGuideRatesForInjectionGroups_(const Group& group);
         /**
          * @brief Updates guide rates for all production groups recursively.