Merge pull request #1750 from ERGO-Code/fix-1691

Fix 1691

check/TestBasis.cpp

@@ -111,7 +111,7 @@ TEST_CASE("set-pathological-basis", "[highs_basis_data]") {
   // Set up a basis with everything nonbasic. This will lead to
   // basic_index being empty when passed to
   // HFactor::setupGeneral. Previously this led to the creation of
-  // pointer &basic_index[0] that caused Windows faiure referenced in
+  // pointer &basic_index[0] that caused Windows failure referenced in
   // #1129, and reported in #1166. However, now that
   // basic_index.data() is used to create the pointer, there is no
   // Windows failure. Within HFactor::setupGeneral and
@@ -156,6 +156,28 @@ TEST_CASE("Basis-no-basic", "[highs_basis_data]") {
   REQUIRE(highs.getModelStatus() == HighsModelStatus::kOptimal);
 }
 
+TEST_CASE("Basis-singular", "[highs_basis_data]") {
+  Highs highs;
+  highs.setOptionValue("output_flag", dev_run);
+  HighsLp lp;
+  lp.num_col_ = 2;
+  lp.num_row_ = 2;
+  lp.col_cost_ = {1, 1};
+  lp.col_lower_ = {0, 0};
+  lp.col_upper_ = {1, 1};
+  lp.row_lower_ = {1, 1};
+  lp.row_upper_ = {2, 2};
+  lp.a_matrix_.start_ = {0, 2, 4};
+  lp.a_matrix_.index_ = {0, 1, 0, 1};
+  lp.a_matrix_.value_ = {1, 2, 2, 4};
+  highs.passModel(lp);
+  HighsBasis basis;
+  REQUIRE(highs.setBasis(basis) == HighsStatus::kError);
+  basis.col_status = {HighsBasisStatus::kBasic, HighsBasisStatus::kBasic};
+  basis.row_status = {HighsBasisStatus::kLower, HighsBasisStatus::kLower};
+  REQUIRE(highs.setBasis(basis) == HighsStatus::kOk);
+}
+
 // No commas in test case name.
 void testBasisReloadModel(Highs& highs, const bool from_file) {
   // Checks that no simplex iterations are required if a saved optimal

check/TestCheckSolution.cpp

@@ -330,6 +330,20 @@ TEST_CASE("check-set-mip-solution-extra-row", "[highs_check_solution]") {
   std::remove(solution_file_name.c_str());
 }
 
+TEST_CASE("check-set-illegal-solution", "[highs_check_solution]") {
+  HighsStatus return_status;
+  std::string model_file =
+      std::string(HIGHS_DIR) + "/check/instances/avgas.mps";
+  Highs highs;
+  highs.setOptionValue("output_flag", dev_run);
+  highs.readModel(model_file);
+  const HighsLp& lp = highs.getLp();
+  HighsSolution solution;
+  REQUIRE(highs.setSolution(solution) == HighsStatus::kError);
+  solution.col_value.assign(lp.num_col_, 0);
+  REQUIRE(highs.setSolution(solution) == HighsStatus::kOk);
+}
+
 void runWriteReadCheckSolution(Highs& highs, const std::string model,
                                const HighsModelStatus require_model_status,
                                const HighsInt write_solution_style) {

src/lp_data/Highs.cpp

@@ -1905,7 +1905,20 @@ HighsStatus Highs::setSolution(const HighsSolution& solution) {
       solution.row_dual.size() >= static_cast<size_t>(model_.lp_.num_row_);
   const bool new_solution = new_primal_solution || new_dual_solution;
 
-  if (new_solution) invalidateUserSolverData();
+  if (new_solution) {
+    invalidateUserSolverData();
+  } else {
+    // Solution is rejected, so give a logging message and error
+    // return
+    highsLogUser(
+        options_.log_options, HighsLogType::kError,
+        "setSolution: User solution is rejected due to mismatch between "
+        "size of col_value and row_dual vectors (%d, %d) and number "
+        "of columns and rows in the model (%d, %d)\n",
+        int(solution.col_value.size()), int(solution.row_dual.size()),
+        int(model_.lp_.num_col_), int(model_.lp_.num_row_));
+    return_status = HighsStatus::kError;
+  }
 
   if (new_primal_solution) {
     solution_.col_value = solution.col_value;
@@ -2052,6 +2065,17 @@ HighsStatus Highs::setBasis(const HighsBasis& basis,
                 : basis.col_status[iCol];
       basis_.alien = false;
     } else {
+      // Check whether a new basis can be defined
+      if (!isBasisRightSize(model_.lp_, basis)) {
+        highsLogUser(
+            options_.log_options, HighsLogType::kError,
+            "setBasis: User basis is rejected due to mismatch between "
+            "size of column and row status vectors (%d, %d) and number "
+            "of columns and rows in the model (%d, %d)\n",
+            int(basis_.col_status.size()), int(basis_.row_status.size()),
+            int(model_.lp_.num_col_), int(model_.lp_.num_row_));
+        return HighsStatus::kError;
+      }
       HighsBasis modifiable_basis = basis;
       modifiable_basis.was_alien = true;
       HighsLpSolverObject solver_object(model_.lp_, modifiable_basis, solution_,