Needs more wotk than I've got time for ATM

Author: jajhall

check/TestQpSolver.cpp

@@ -1138,3 +1138,31 @@ TEST_CASE("rowless-qp", "[qpsolver]") {
 
   highs.resetGlobalScheduler(true);
 }
+
+TEST_CASE("2489", "[qpsolver]") {
+  // This QP is
+  //
+  // Min, x^2/2 + x
+  //
+  // 0*x + 0*y <= 1
+  //
+  // -10 <= (x, y) <= 10
+  //
+  // Hence it has a constraint, but its coefficients are zero
+  Highs h;
+  //  h.setOptionValue("output_flag", dev_run);
+  assert(h.setOptionValue("log_dev_level", 3) == HighsStatus::kOk);
+  assert(h.addCol(1.0, -10.0, 10.0, 0, NULL, NULL) == HighsStatus::kOk);
+  assert(h.addCol(0.0, -10.0, 10.0, 0, NULL, NULL) == HighsStatus::kOk);
+  assert(h.addRow(0.0, 0.0, 0, NULL, NULL) == HighsStatus::kOk);
+  HighsHessian hessian;
+  hessian.dim_ = 1;
+  hessian.format_ = HessianFormat::kTriangular;
+  hessian.start_ = {0, 1};
+  hessian.index_ = {0};
+  hessian.value_ = {1.0};
+  assert(h.passHessian(hessian) == HighsStatus::kOk);
+  assert(h.run() == HighsStatus::kOk);
+
+  h.resetGlobalScheduler(true);
+}

highs/interfaces/highs_c_api.cpp

@@ -108,7 +108,7 @@ HighsInt Highs_mipCall(const HighsInt num_col, const HighsInt num_row,
   }
 
   highs.resetGlobalScheduler(true);
-  
+
   return (HighsInt)status;
 }
 
@@ -173,9 +173,9 @@ HighsInt Highs_qpCall(
 
 void* Highs_create(void) { return new Highs(); }
 
-void Highs_destroy(void* highs) { 
+void Highs_destroy(void* highs) {
   Highs::resetGlobalScheduler(true);
-  delete (Highs*)highs; 
+  delete (Highs*)highs;
 }
 
 const char* Highs_version(void) { return highsVersion(); }

highs/model/HighsHessianUtils.cpp

@@ -131,10 +131,11 @@ void completeHessianDiagonal(const HighsOptions& options,
       num_missing_diagonal_entries++;
     }
   }
-  highsLogDev(options.log_options, HighsLogType::kInfo,
-              "Hessian has dimension %d and %d nonzeros: inserting %d zeros "
-              "onto the diagonal\n",
-              (int)dim, (int)num_nz, (int)num_missing_diagonal_entries);
+  if (num_missing_diagonal_entries > 0)
+    highsLogDev(options.log_options, HighsLogType::kInfo,
+                "Hessian has dimension %d and %d nonzeros: inserting %d zeros "
+                "onto the diagonal\n",
+                int(dim), int(num_nz), int(num_missing_diagonal_entries));
   assert(num_missing_diagonal_entries >= dim - num_nz);
   if (!num_missing_diagonal_entries) return;
   // There are missing diagonal entries to be inserted as explicit zeros

highs/qpsolver/basis.cpp

@@ -57,16 +57,6 @@ void Basis::build() {
     baseindex[counter++] = i;
   }
 
-  const bool empty_matrix = (int)Atran.index.size() == 0;
-  if (empty_matrix) {
-    // The index/value vectors have size zero if the matrix has no
-    // columns. However, in the Windows build, referring to index 0 of a
-    // vector of size zero causes a failure, so resize to 1 to prevent
-    // this.
-    assert(Atran.num_col == 0);
-    Atran.index.resize(1);
-    Atran.value.resize(1);
-  }
   basisfactor.setup(Atran.num_col, Atran.num_row, Atran.start.data(),
                     Atran.index.data(), Atran.value.data(), baseindex.data());
   basisfactor.build();