Fix 2419

FEATURES.md

@@ -6,4 +6,6 @@ Forcing column reduction now checks the bound on the column dual rather than whe
 
 Now handling correctly the case where an infeasible MIP has a feasible relaxation, so no ray is computed fixing [#2415](https://github.com/ERGO-Code/HiGHS/issues/2415)
 
+Fixed minor bug exposed by [#2441](https://github.com/ERGO-Code/HiGHS/issues/2441) in Highs::setSolution() for a sparse user solution when the moidel is empty, and only clearing the dual data before solving with modified objective in Highs::multiobjectiveSolve() so that user-supplied solution is not cleared.
+
 

highs/Highs.h

@@ -90,6 +90,11 @@ class Highs {
    */
   HighsStatus clearSolver();
 
+  /**
+   * @brief Clear all dual data associated with the model
+   */
+  HighsStatus clearSolverDualData();
+
   /**
    * Methods for model input
    */
@@ -1542,6 +1547,12 @@ class Highs {
   // invalidateRanging(), invalidateInfo(), invalidateEkk() and
   // invalidateIis()
   void invalidateSolverData();
+
+  // Invalidates all solver dual data in Highs class members by calling
+  // invalidateModelStatus(), invalidateRanging(), and invalidateInfo()
+  //
+  // Used when only the objective changes
+  void invalidateSolverDualData();
   //
   // Invalidates the model status, solution_ and info_
   void invalidateModelStatusSolutionAndInfo();

highs/lp_data/Highs.cpp

@@ -67,6 +67,13 @@ HighsStatus Highs::clearSolver() {
   return returnFromHighs(return_status);
 }
 
+HighsStatus Highs::clearSolverDualData() {
+  HighsStatus return_status = HighsStatus::kOk;
+  clearDerivedModelProperties();
+  invalidateSolverDualData();
+  return returnFromHighs(return_status);
+}
+
 HighsStatus Highs::setOptionValue(const std::string& option, const bool value) {
   if (setLocalOptionValue(options_.log_options, option, options_.records,
                           value) == OptionStatus::kOk)
@@ -2261,16 +2268,17 @@ HighsStatus Highs::setSolution(const HighsSolution& solution) {
 HighsStatus Highs::setSolution(const HighsInt num_entries,
                                const HighsInt* index, const double* value) {
   HighsStatus return_status = HighsStatus::kOk;
+  if (model_.lp_.num_col_ == 0) return return_status;
   // Warn about duplicates in index
   HighsInt num_duplicates = 0;
   std::vector<bool> is_set;
   is_set.assign(model_.lp_.num_col_, false);
   for (HighsInt iX = 0; iX < num_entries; iX++) {
     HighsInt iCol = index[iX];
-    if (iCol < 0 || iCol > model_.lp_.num_col_) {
+    if (iCol < 0 || iCol >= model_.lp_.num_col_) {
       highsLogUser(options_.log_options, HighsLogType::kError,
                    "setSolution: User solution index %d has value %d out of "
-                   "range [0, %d)",
+                   "range [0, %d)\n",
                    int(iX), int(iCol), int(model_.lp_.num_col_));
       return HighsStatus::kError;
     } else if (value[iX] < model_.lp_.col_lower_[iCol] -
@@ -2280,7 +2288,7 @@ HighsStatus Highs::setSolution(const HighsInt num_entries,
                    value[iX]) {
       highsLogUser(options_.log_options, HighsLogType::kError,
                    "setSolution: User solution value %d of %g is infeasible "
-                   "for bounds [%g, %g]",
+                   "for bounds [%g, %g]\n",
                    int(iX), value[iX], model_.lp_.col_lower_[iCol],
                    model_.lp_.col_upper_[iCol]);
       return HighsStatus::kError;
@@ -3634,15 +3642,19 @@ void Highs::clearStandardFormLp() {
 }
 
 void Highs::invalidateSolverData() {
-  invalidateModelStatus();
+  invalidateSolverDualData();
   invalidateSolution();
   invalidateBasis();
-  invalidateRanging();
-  invalidateInfo();
   invalidateEkk();
   invalidateIis();
 }
 
+void Highs::invalidateSolverDualData() {
+  invalidateModelStatus();
+  invalidateRanging();
+  invalidateInfo();
+}
+
 void Highs::invalidateModelStatusSolutionAndInfo() {
   invalidateModelStatus();
   invalidateSolution();

highs/lp_data/HighsInterface.cpp

@@ -3948,7 +3948,12 @@ HighsStatus Highs::multiobjectiveSolve() {
     highsLogUser(options_.log_options, HighsLogType::kInfo, "%s",
                  multi_objective_log->str().c_str());
   }
-  this->clearSolver();
+  // Solving with a different objective, but don't call
+  // this->clearSolver() since this loses the current solution - that
+  // may have been provided by the user (#2419). Just clear the dual
+  // data.
+  //
+  this->clearSolverDualData();
   if (this->options_.blend_multi_objectives) {
     // Objectives are blended by weight and minimized
     lp.offset_ = 0;