Fix lag in updating output variables

This addresses an issue with lag between the time of setting an input
via and actuator, and seeing the corresponding output variable change.
This commit specifically addresses the issue for output variables
related to the zone air heat balance, and for internal heat gains. Other
output variables may still suffer from the lag issue, however they can
be handled in a similar manner by simply calling their respective update
functions. In the future we will introduce an explicit list of supported
output variables, at which time we can have positive confirmation that
we have addressed the lag for all supported output variables.

close lbl-srg/modelica-buildings/#1681

epfmi/EPComponent.cpp

@@ -8,6 +8,8 @@
 #include "EnergyPlus/DataHeatBalFanSys.hh"
 #include "EnergyPlus/DataRuntimeLanguage.hh"
 #include "EnergyPlus/EMSManager.hh"
+#include "EnergyPlus/HeatBalanceAirManager.hh"
+#include "EnergyPlus/InternalHeatGains.hh"
 #include "EnergyPlus/OutputProcessor.hh"
 #include "EnergyPlus/ZoneTempPredictorCorrector.hh"
 
@@ -192,6 +194,7 @@ void EPComponent::exchange()
     resetActuator(h);
   };
 
+  // Update inputs first, then outputs so that we can do some updates within EnergyPlus
   for( auto & varmap : variables ) {
     auto & var = varmap.second;
     auto varZoneNum = zoneNum(var.name);
@@ -203,6 +206,36 @@ void EPComponent::exchange()
           EnergyPlus::DataHeatBalFanSys::MAT( varZoneNum ) = var.value;
         }
         break;
+      case VariableType::EMS_ACTUATOR:
+        if( var.valueset ) {
+          compSetActuatorValue(
+            var.actuatorcomponentkey,
+            var.actuatorcomponenttype,
+            var.actuatorcontroltype,
+            var.value
+          );
+        } else {
+          compResetActuator(
+            var.actuatorcomponentkey,
+            var.actuatorcomponenttype,
+            var.actuatorcontroltype
+          );
+        }
+        break;
+      default:
+        break;
+    }
+  }
+
+  // Run some internal EnergyPlus functions to update outputs
+  EnergyPlus::HeatBalanceAirManager::ReportZoneMeanAirTemp();
+  EnergyPlus::InternalHeatGains::InitInternalHeatGains();
+
+  // Now update the outputs
+  for( auto & varmap : variables ) {
+    auto & var = varmap.second;
+    auto varZoneNum = zoneNum(var.name);
+    switch ( var.type ) {
       case VariableType::V:
         var.value = EnergyPlus::DataHeatBalance::Zone( varZoneNum ).Volume;
         var.valueset = true;
@@ -223,22 +256,6 @@ void EPComponent::exchange()
         var.value = getSensorValue(var);
         var.valueset = true;
         break;
-      case VariableType::EMS_ACTUATOR:
-        if( var.valueset ) {
-          compSetActuatorValue(
-            var.actuatorcomponentkey,
-            var.actuatorcomponenttype,
-            var.actuatorcontroltype,
-            var.value
-          );
-        } else {
-          compResetActuator(
-            var.actuatorcomponentkey,
-            var.actuatorcomponenttype,
-            var.actuatorcontroltype
-          );
-        }
-        break;
       default:
         break;
     }