From 24e8d5b2c5eb643cc5e609a8d6ec5d4c3de8e7d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Florian=20Omn=C3=A8s?= <florian.omnes@rte-france.com>
Date: Tue, 10 Jan 2023 17:19:57 +0100
Subject: [PATCH] Restore warm start for OR-Tools+XPRESS (#1079)

---
 src/solver/utils/named_problem.h   |  1 -
 src/solver/utils/ortools_utils.cpp | 22 +++++++++++++++++-----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/solver/utils/named_problem.h b/src/solver/utils/named_problem.h
index 59a338b0cb..c83fa7d32d 100644
--- a/src/solver/utils/named_problem.h
+++ b/src/solver/utils/named_problem.h
@@ -26,7 +26,6 @@ struct PROBLEME_SIMPLEXE_NOMME : public PROBLEME_SIMPLEXE
 
     bool isMIP() const;
     bool basisExists() const;
-    mutable bool solverSupportsWarmStart = false;
 };
 } // namespace Optimization
 } // namespace Antares
diff --git a/src/solver/utils/ortools_utils.cpp b/src/solver/utils/ortools_utils.cpp
index c18ce82db9..b6b4552ec1 100644
--- a/src/solver/utils/ortools_utils.cpp
+++ b/src/solver/utils/ortools_utils.cpp
@@ -116,6 +116,20 @@ static void tuneSolverSpecificOptions(MPSolver* solver)
     }
 }
 
+static bool solverSupportsWarmStart(const MPSolver* solver)
+{
+    if (!solver)
+        return false;
+
+    switch (solver->ProblemType())
+    {
+    case MPSolver::XPRESS_LINEAR_PROGRAMMING:
+        return true;
+    default:
+        return false;
+    }
+}
+
 namespace Antares
 {
 namespace Optimization
@@ -286,8 +300,9 @@ MPSolver* ORTOOLS_Simplexe(Antares::Optimization::PROBLEME_SIMPLEXE_NOMME* Probl
                            bool keepBasis)
 {
     MPSolverParameters params;
+    bool warmStart = solverSupportsWarmStart(solver);
     // Provide an initial simplex basis, if any
-    if (Probleme->basisExists() && !Probleme->isMIP() && Probleme->solverSupportsWarmStart)
+    if (warmStart && Probleme->basisExists() && !Probleme->isMIP())
     {
         solver->SetStartingLpBasisInt(Probleme->StatutDesVariables, Probleme->StatutDesContraintes);
     }
@@ -296,7 +311,7 @@ MPSolver* ORTOOLS_Simplexe(Antares::Optimization::PROBLEME_SIMPLEXE_NOMME* Probl
     {
         extract_from_MPSolver(solver, Probleme);
         // Save the final simplex basis for next resolutions
-        if (keepBasis && !Probleme->isMIP() && Probleme->solverSupportsWarmStart)
+        if (warmStart && keepBasis && !Probleme->isMIP())
         {
             solver->GetFinalLpBasisInt(Probleme->StatutDesVariables,
                                        Probleme->StatutDesContraintes);
@@ -388,8 +403,5 @@ MPSolver* MPSolverFactory(const Antares::Optimization::PROBLEME_SIMPLEXE_NOMME*
         AntaresSolverEmergencyShutdown();
     }
 
-    if (solverName == "xpress")
-        probleme->solverSupportsWarmStart = true;
-
     return solver;
 }