Standard form conversion now works for maximizations

check/TestLpSolvers.cpp

@@ -2,7 +2,7 @@
 #include "Highs.h"
 #include "catch.hpp"
 
-const bool dev_run = false;
+const bool dev_run = true;  // false;
 
 struct IterationCount {
   HighsInt simplex;
@@ -474,6 +474,7 @@ TEST_CASE("blending-lp-ipm", "[highs_lp_solver]") {
 void testStandardForm(const HighsLp& lp) {
   Highs highs;
   highs.setOptionValue("output_flag", dev_run);
+  HighsInt sense = HighsInt(lp.sense_);
   highs.passModel(lp);
   highs.run();
   //  highs.writeSolution("", kSolutionStylePretty);
@@ -513,7 +514,8 @@ void testStandardForm(const HighsLp& lp) {
   REQUIRE(highs.run() == HighsStatus::kOk);
   REQUIRE(highs.getModelStatus() == HighsModelStatus::kOptimal);
   highs.writeSolution("", kSolutionStylePretty);
-  double objective_function_value = highs.getInfo().objective_function_value;
+  double objective_function_value =
+      sense * highs.getInfo().objective_function_value;
   double objective_difference =
       std::fabs(objective_function_value - required_objective_function_value) /
       std::max(1.0, std::fabs(required_objective_function_value));
@@ -567,7 +569,7 @@ TEST_CASE("standard-form-lp", "[highs_lp_solver]") {
 
   std::vector<HighsInt> index;
   std::vector<double> value;
-  // Add a fixed column and a fixed row
+  // Add a fixed column and a fixed row, and maximize
   highs.passModel(lp);
   index = {0, 1, 2};
   value = {-1, 1, -1};
@@ -577,6 +579,8 @@ TEST_CASE("standard-form-lp", "[highs_lp_solver]") {
   value = {-2, -1, 1, 3};
   REQUIRE(highs.addRow(1.0, 1.0, 4, index.data(), value.data()) ==
           HighsStatus::kOk);
-
+  REQUIRE(highs.changeObjectiveSense(ObjSense::kMaximize) == HighsStatus::kOk);
+  printf(
+      "\nNow test by adding a fixed column and a fixed row, and maximizing\n");
   testStandardForm(highs.getLp());
 }

src/lp_data/HighsInterface.cpp

@@ -31,8 +31,13 @@ HighsStatus Highs::formStandardFormLp() {
   // boxed rows can be transformed to pairs of one-sided rows,
   // requiring the standard form matrix to be row-wise. The original
   // columns are assumed to come before any new columns, so their
-  // costs must be defined befor costs of new columns.
-  this->standard_form_cost_ = lp.col_cost_;
+  // costs (as a minimization) must be defined befor costs of new
+  // columns.
+  // Determine the objective scaling, and apply it to any offset
+  HighsInt sense = HighsInt(lp.sense_);
+  this->standard_form_offset_ = sense * lp.offset_;
+  for (HighsInt iCol = 0; iCol < lp.num_col_; iCol++)
+    this->standard_form_cost_.push_back(sense * lp.col_cost_[iCol]);
   this->standard_form_matrix_.format_ = MatrixFormat::kRowwise;
   this->standard_form_matrix_.num_col_ = lp.num_col_;
   // Create a HighsSparseMatrix instance to store rows extracted from
@@ -143,12 +148,9 @@ HighsStatus Highs::formStandardFormLp() {
   // can be added
   matrix.ensureColwise();
   this->standard_form_matrix_.ensureColwise();
-  // Determine the objective scaling, and apply it to any offset
-  double objective_mu = double(lp.sense_);
-  this->standard_form_offset_ = objective_mu * lp.offset_;
   // Work through the columns, ensuring that all have non-negativity bounds
   for (HighsInt iCol = 0; iCol < lp.num_col_; iCol++) {
-    double cost = objective_mu * lp.col_cost_[iCol];
+    double cost = sense * lp.col_cost_[iCol];
     double lower = lp.col_lower_[iCol];
     double upper = lp.col_upper_[iCol];
     if (lower > -kHighsInf) {