From 88488b234dbb0387a08f690fa6d22db47621efc6 Mon Sep 17 00:00:00 2001
From: Ted Ralphs <ted@lehigh.edu>
Date: Fri, 29 Nov 2024 16:38:55 +0100
Subject: [PATCH] Allowing branching on linking variables even when doing
 fractional branching to accpount for some cases where cut generation fails

---
 src/MibSBranchStrategyPseudo.cpp | 15 +++++++++++++--
 src/MibSCutGenerator.cpp         | 14 +++++++-------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/MibSBranchStrategyPseudo.cpp b/src/MibSBranchStrategyPseudo.cpp
index 4ba5efd3..d6aba9e0 100644
--- a/src/MibSBranchStrategyPseudo.cpp
+++ b/src/MibSBranchStrategyPseudo.cpp
@@ -158,17 +158,28 @@ MibSBranchStrategyPseudo::createCandBranchObjects(int numPassesLeft, double ub)
        }
     }
     
-    // Check for fractional lower level variables variables
+    // Check for fractional lower level variables
     if(branchPar == MibSBranchingStrategyLower){
        for (i = 0; i < numCols; ++i) {
           if (fabs(floor(solution[i] + 0.5) - solution[i]) > etol &&
-              varType[i] == MibSVarLower){
+              varType[i] == MibSVarLower && colType[i] == 'C'){
              fractionalLowerVar = true;
              break;
           }
        }
     }
     
+    // Check for fractional variables overall
+    if(branchPar == MibSBranchingStrategyFractional){
+       for (i = 0; i < numCols; ++i) {
+          if (fabs(floor(solution[i] + 0.5) - solution[i]) > etol &&
+              colType[i] != 'C'){
+             branchPar = MibSBranchingStrategyLinking;
+             break;
+          }
+       }
+    }
+
     for (i = 0; i < numCols; ++i) {
        if(colType[i] == 'C'){
           candidate[i] = false;
diff --git a/src/MibSCutGenerator.cpp b/src/MibSCutGenerator.cpp
index 35856d2a..314174ee 100644
--- a/src/MibSCutGenerator.cpp
+++ b/src/MibSCutGenerator.cpp
@@ -1245,7 +1245,7 @@ MibSCutGenerator::solveModelIC(double *uselessIneqs, double *ray, double *rhs,
 	}
     }
 
-    assert(alphaUb >= 0);
+    //assert(alphaUb >= 0);
 
     if(isUnbounded == false){
 	alpha = alphaUb;
@@ -6062,7 +6062,7 @@ MibSCutGenerator::generateConstraints(BcpsConstraintPool &conPool)
         if (localModel_->MibSPar_->entry(MibSParams::bilevelFreeSetTypeISIC) ==
             MibSBilevelFreeSetTypeISICWithLLOptSol && haveSecondLevelSol &&
             relaxedObjVal <= localModel_->bS_->objVal_ + localModel_->etol_){
-           localModel_->counterFracISICFail_++;
+           localModel_->counterLIntISICFail_++;
         }else if ((localModel_->MibSPar_->entry(MibSParams::bilevelFreeSetTypeISIC) ==
                    MibSBilevelFreeSetTypeISICWithLLOptSol && haveSecondLevelSol) ||
                   localModel_->MibSPar_->entry(MibSParams::bilevelFreeSetTypeISIC) ==
@@ -6070,9 +6070,9 @@ MibSCutGenerator::generateConstraints(BcpsConstraintPool &conPool)
            cutType = MibSIntersectionCutImprovingSolution;
            returnVal = intersectionCuts(conPool, bS->optLowerSolutionOrd_, cutType);
            if (returnVal){
-              localModel_->counterFracISIC_++;
+              localModel_->counterLIntISIC_++;
            }else{
-              localModel_->counterFracISICFail_++;
+              localModel_->counterLIntISICFail_++;
            }
            numCuts += returnVal;
         }
@@ -6127,7 +6127,7 @@ MibSCutGenerator::generateConstraints(BcpsConstraintPool &conPool)
         if (localModel_->MibSPar_->entry(MibSParams::bilevelFreeSetTypeISIC) ==
             MibSBilevelFreeSetTypeISICWithLLOptSol && haveSecondLevelSol &&
             relaxedObjVal <= localModel_->bS_->objVal_ + localModel_->etol_){
-           localModel_->counterFracISICFail_++;
+           localModel_->counterYIntISICFail_++;
         }else if ((localModel_->MibSPar_->entry(MibSParams::bilevelFreeSetTypeISIC) ==
                    MibSBilevelFreeSetTypeISICWithLLOptSol && haveSecondLevelSol) ||
                   localModel_->MibSPar_->entry(MibSParams::bilevelFreeSetTypeISIC) ==
@@ -6135,9 +6135,9 @@ MibSCutGenerator::generateConstraints(BcpsConstraintPool &conPool)
            cutType = MibSIntersectionCutImprovingSolution;
            returnVal = intersectionCuts(conPool, bS->optLowerSolutionOrd_, cutType);
            if (returnVal){
-              localModel_->counterFracISIC_++;
+              localModel_->counterYIntISIC_++;
            }else{
-              localModel_->counterFracISICFail_++;
+              localModel_->counterYIntISICFail_++;
            }
            numCuts += returnVal;
         }