Complete HiGHS v1.12.0 integration and fix references

MODULE.bazel

@@ -44,7 +44,7 @@ bazel_dep(name = "eigen", version = "3.4.0.bcr.3")
 bazel_dep(name = "glpk", version = "5.0.bcr.4")
 bazel_dep(name = "google_benchmark", version = "1.9.2")
 bazel_dep(name = "googletest", version = "1.17.0")
-bazel_dep(name = "highs", version = "1.11.0")
+bazel_dep(name = "highs", version = "1.12.0")
 bazel_dep(name = "protobuf-matchers", version = "0.1.1")
 bazel_dep(name = "protobuf", version = "32.0")
 bazel_dep(name = "re2", version = "2025-08-12")

examples/cpp/uncapacitated_facility_location.cc

@@ -211,6 +211,11 @@ void RunAllExamples(int32_t facilities, int32_t clients, double fix_cost) {
   UncapacitatedFacilityLocation(facilities, clients, fix_cost,
                                 MPSolver::GLPK_MIXED_INTEGER_PROGRAMMING);
 #endif
+#if defined(USE_HIGHS)
+  LOG(INFO) << "---- Integer programming example with HiGHS ----";
+  UncapacitatedFacilityLocation(facilities, clients, fix_cost,
+                                MPSolver::HIGHS_MIXED_INTEGER_PROGRAMMING);
+#endif
 #if defined(USE_SCIP)
   LOG(INFO) << "---- Integer programming example with SCIP ----";
   UncapacitatedFacilityLocation(facilities, clients, fix_cost,

makefiles/Makefile.cpp.mk

@@ -603,6 +603,7 @@ detect_cpp:
 	@echo USE_COINOR = $(USE_COINOR)
 	@echo USE_SCIP = $(USE_SCIP)
 	@echo USE_GLPK = $(USE_GLPK)
+	@echo USE_HIGHS = $(USE_HIGHS)
 	@echo USE_CPLEX = $(USE_CPLEX)
 ifdef GLPK_ROOT
 	@echo GLPK_ROOT = $(GLPK_ROOT)

or-tools.code-workspace

@@ -109,6 +109,7 @@
     "USE_GLOP",
     "USE_CLP",
     "USE_CBC",
+    "USE_HIGHS",
     "USE_PDLP",
     "USE_SCIP"
     ],

ortools/graph/christofides.h

@@ -57,9 +57,9 @@ class ChristofidesPathSolver {
  public:
   enum class MatchingAlgorithm {
     MINIMUM_WEIGHT_MATCHING,
-#if defined(USE_CBC) || defined(USE_SCIP)
+#if defined(USE_CBC) || defined(USE_SCIP) || defined(USE_HIGHS)
     MINIMUM_WEIGHT_MATCHING_WITH_MIP,
-#endif  // defined(USE_CBC) || defined(USE_SCIP)
+#endif  // defined(USE_CBC) || defined(USE_SCIP) || defined(USE_HIGHS)
     MINIMAL_WEIGHT_MATCHING,
   };
   ChristofidesPathSolver(NodeIndex num_nodes, CostFunction costs);
@@ -155,7 +155,7 @@ ComputeMinimumWeightMatching(const GraphType& graph,
   return match;
 }
 
-#if defined(USE_CBC) || defined(USE_SCIP)
+#if defined(USE_CBC) || defined(USE_SCIP) || defined(USE_HIGHS)
 // Computes a minimum weight perfect matching on an undirected graph using a
 // Mixed Integer Programming model.
 // TODO(user): Handle infeasible cases if this algorithm is used outside of
@@ -211,6 +211,9 @@ ComputeMinimumWeightMatchingWithMIP(const GraphType& graph,
 #if defined(USE_SCIP)
   MPSolver mp_solver("MatchingWithSCIP",
                      MPSolver::SCIP_MIXED_INTEGER_PROGRAMMING);
+#elif defined(USE_HIGHS)
+  MPSolver mp_solver("MatchingWithHiGHS",
+                     MPSolver::HIGHS_MIXED_INTEGER_PROGRAMMING);
 #elif defined(USE_CBC)
   MPSolver mp_solver("MatchingWithCBC",
                      MPSolver::CBC_MIXED_INTEGER_PROGRAMMING);
@@ -330,7 +333,7 @@ ChristofidesPathSolver<CostType, ArcIndex, NodeIndex, CostFunction>::Solve() {
       result->swap(closure_arcs);
       break;
     }
-#endif  // defined(USE_CBC) || defined(USE_SCIP)
+#endif  // defined(USE_CBC) || defined(USE_SCIP) || defined(USE_HIGHS)
     case MatchingAlgorithm::MINIMAL_WEIGHT_MATCHING: {
       // TODO(user): Cost caching was added and can gain up to 20% but
       // increases memory usage; see if we can avoid caching.

ortools/linear_solver/highs_interface.cc

@@ -225,13 +225,13 @@ int64_t HighsInterface::nodes() const {
 }
 
 MPSolver::BasisStatus HighsInterface::row_status(int constraint_index) const {
-  // TODO(user): While basis status isn't well defined for PDLP, we could
+  // TODO(user): While basis status isn't well defined for HiGHS, we could
   // guess statuses that might be useful.
   return MPSolver::BasisStatus::FREE;
 }
 
 MPSolver::BasisStatus HighsInterface::column_status(int variable_index) const {
-  // TODO(user): While basis status isn't well defined for PDLP, we could
+  // TODO(user): While basis status isn't well defined for HiGHS, we could
   // guess statuses that might be useful.
   return MPSolver::BasisStatus::FREE;
 }
@@ -242,10 +242,10 @@ bool HighsInterface::IsLP() const { return true; }
 
 bool HighsInterface::IsMIP() const { return solve_as_a_mip_; }
 
-std::string HighsInterface::SolverVersion() const { return "PDLP Solver"; }
+std::string HighsInterface::SolverVersion() const { return "HiGHS Solver"; }
 
 // TODO(user): Consider returning the SolveLog here, as it could be essential
-// for interpreting the PDLP solution.
+// for interpreting the HiGHS solution.
 void* HighsInterface::underlying_solver() { return nullptr; }
 
 void HighsInterface::ExtractNewVariables() { NonIncrementalChange(); }