From 1f3834b6c489cc3e39b495a81bd98b5e8057ed17 Mon Sep 17 00:00:00 2001
From: Yu Xie <yux616@lehigh.edu>
Date: Thu, 30 Nov 2023 22:15:38 -0500
Subject: [PATCH] skip IDIC if the generation prob. has all zero sol

---
 src/MibSCutGenerator.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/MibSCutGenerator.cpp b/src/MibSCutGenerator.cpp
index c9c28090..aa0e8e54 100644
--- a/src/MibSCutGenerator.cpp
+++ b/src/MibSCutGenerator.cpp
@@ -1279,6 +1279,7 @@ MibSCutGenerator::findLowerLevelSolImprovingDirectionIC(double *uselessIneqs, do
     OsiSolverInterface *oSolver = localModel_->solver();
     double infinity(oSolver->getInfinity());
     bool getA2G2Matrix(false), getG2Matrix(false);
+    bool solErr(true);
     int i;
     int rowIndex(0), colIndex(0), cntInt(0);
     double rhs(0.0), value(0.0);
@@ -1524,8 +1525,17 @@ MibSCutGenerator::findLowerLevelSolImprovingDirectionIC(double *uselessIneqs, do
     else if(nSolver->isProvenOptimal()){
 	const double *optSol = nSolver->getColSolution();
 	CoinDisjointCopyN(optSol, lCols, lowerLevelSol);
-	CoinDisjointCopyN(optSol + lCols, numContCols, uselessIneqs);
+      // YX: numerical issue; skip if the lowerLevelSol found is all zero
+      for(i = 0; i < lCols; i++){
+        if(fabs(lowerLevelSol[i]) > 0){
+          solErr = false;
+          break;
+        }
+      }
+      if(!solErr){
+        CoinDisjointCopyN(optSol + lCols, numContCols, uselessIneqs);
         foundSolution = true;
+      }
     }
     delete [] lCoeffsTimesLpSol;
     return foundSolution;