try using a shorter termination for bisection solver

Author: yujiex

src/EnergyPlus/ExtendedHI.cc

@@ -485,7 +485,7 @@ namespace ExtendedHI {
         // The function computes the extended heat index, in Kelvinn
 
         auto const HVACSystemRootSolverBackup = state.dataRootFinder->HVACSystemRootFinding.HVACSystemRootSolver;
-        state.dataRootFinder->HVACSystemRootFinding.HVACSystemRootSolver = HVACSystemRootSolverAlgorithm::BisectionThenRegulaFalsi;
+        state.dataRootFinder->HVACSystemRootFinding.HVACSystemRootSolver = HVACSystemRootSolverAlgorithm::ShortBisectionThenRegulaFalsi;
         int eqvar_name = 0;
         Real64 eqvar_value = find_eqvar_name_and_value(state, Ta, RH, eqvar_name);
 

src/EnergyPlus/General.cc

@@ -241,6 +241,14 @@ void SolveRoot(const EnergyPlusData &state,
             }
             break;
         }
+        case HVACSystemRootSolverAlgorithm::ShortBisectionThenRegulaFalsi: {
+            if (NIte < 3) {
+                XTemp = (X1 + X0) / 2.0;
+            } else {
+                XTemp = (Y0 * X1 - Y1 * X0) / DY;
+            }
+            break;
+        }
         default: {
             XTemp = (Y0 * X1 - Y1 * X0) / DY;
         }

src/EnergyPlus/HVACSystemRootFindingAlgorithm.hh

@@ -59,6 +59,7 @@ enum class HVACSystemRootSolverAlgorithm : int
     RegulaFalsiThenBisection,
     BisectionThenRegulaFalsi,
     Alternation,
+    ShortBisectionThenRegulaFalsi,
     Num
 };
 struct HVACSystemRootFindingAlgorithm