Merge pull request #1742 from ERGO-Code/fix-1724

Now calling saveReportMipSolution when presolve reduces MIP to empty
ERGO-Code · May 7, 2024 · d146930 · d146930
2 parents 0bd3176 + 053a624
commit d146930
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Showing 4 changed files with 39 additions and 11 deletions.
diff --git a/check/TestMipSolver.cpp b/check/TestMipSolver.cpp
@@ -616,6 +616,43 @@ TEST_CASE("MIP-max-offset-test", "[highs_test_mip_solver]") {
                       dev_run));
 }
 
+TEST_CASE("MIP-get-saved-solutions-presolve", "[highs_test_mip_solver]") {
+  const std::string solution_file = "MipImproving.sol";
+  Highs highs;
+  highs.setOptionValue("output_flag", dev_run);
+  highs.setOptionValue("mip_improving_solution_save", true);
+  highs.setOptionValue("mip_improving_solution_report_sparse", true);
+  highs.setOptionValue("mip_improving_solution_file", solution_file);
+  // #1724: Add row to the example so that solution is non-zero
+  HighsLp lp;
+  lp.num_col_ = 2;
+  lp.num_row_ = 1;
+  lp.col_cost_ = {1, 1};
+  lp.col_lower_ = {0, 0};
+  lp.col_upper_ = {1, 1};
+  lp.integrality_ = {HighsVarType::kInteger, HighsVarType::kInteger};
+  lp.row_lower_ = {1};
+  lp.row_upper_ = {kHighsInf};
+  lp.a_matrix_.num_col_ = 2;
+  lp.a_matrix_.num_row_ = 1;
+  lp.a_matrix_.start_ = {0, 1, 1};
+  lp.a_matrix_.index_ = {0};
+  lp.a_matrix_.value_ = {1};
+  highs.passModel(lp);
+  highs.run();
+  const std::vector<HighsObjectiveSolution> saved_objective_and_solution =
+      highs.getSavedMipSolutions();
+  const HighsInt num_saved_solution = saved_objective_and_solution.size();
+  REQUIRE(num_saved_solution == 1);
+  const HighsInt last_saved_solution = num_saved_solution - 1;
+  REQUIRE(saved_objective_and_solution[last_saved_solution].objective ==
+          highs.getInfo().objective_function_value);
+  for (HighsInt iCol = 0; iCol < highs.getLp().num_col_; iCol++)
+    REQUIRE(saved_objective_and_solution[last_saved_solution].col_value[iCol] ==
+            highs.getSolution().col_value[iCol]);
+  std::remove(solution_file.c_str());
+}
+
 bool objectiveOk(const double optimal_objective,
                  const double require_optimal_objective, const bool dev_run) {
   double error = std::fabs(optimal_objective - require_optimal_objective) /

diff --git a/src/mip/HighsMipSolver.cpp b/src/mip/HighsMipSolver.cpp
@@ -128,6 +128,7 @@ void HighsMipSolver::run() {
       mipdata_->lower_bound = 0;
       mipdata_->upper_bound = 0;
       mipdata_->transformNewIntegerFeasibleSolution(std::vector<double>());
+      mipdata_->saveReportMipSolution();
     }
     cleanupSolve();
     return;

diff --git a/src/mip/HighsMipSolverData.cpp b/src/mip/HighsMipSolverData.cpp
@@ -1908,16 +1908,6 @@ void HighsMipSolverData::saveReportMipSolution(const double new_upper_limit) {
   if (mipsolver.submip) return;
   if (non_improving) return;
 
-  /*
-  printf(
-      "%7s dimension(%d, %d) "
-      "%4simproving solution: numImprovingSols = %4d; Limits (%11.4g, "
-      "%11.4g); Objective = %11.4g\n",
-      mipsolver.submip ? "Sub-MIP" : "MIP    ", mipsolver.model_->num_col_,
-      mipsolver.model_->num_row_, non_improving ? "non-" : "",
-      int(numImprovingSols), new_upper_limit, upper_limit,
-      mipsolver.solution_objective_);
-  */
   if (mipsolver.callback_->user_callback) {
     if (mipsolver.callback_->active[kCallbackMipImprovingSolution]) {
       mipsolver.callback_->clearHighsCallbackDataOut();

diff --git a/src/mip/HighsMipSolverData.h b/src/mip/HighsMipSolverData.h
@@ -158,7 +158,7 @@ struct HighsMipSolverData {
   void checkObjIntegrality();
   void runPresolve(const HighsInt presolve_reduction_limit);
   void setupDomainPropagation();
-  void saveReportMipSolution(const double new_upper_limit);
+  void saveReportMipSolution(const double new_upper_limit = -kHighsInf);
   void runSetup();
   double transformNewIntegerFeasibleSolution(
       const std::vector<double>& sol,