Add test to expose C api failure

Author: filikat

check/TestHighsParallel.cpp

@@ -7,6 +7,7 @@
 #include <iostream>
 
 #include "catch.hpp"
+#include "interfaces/highs_c_api.h"
 #include "matrix_multiplication.hpp"
 #include "parallel/HighsParallel.h"
 
@@ -305,4 +306,48 @@ TEST_CASE("CancelNestedTasks", "[parallel]") {
   }
 
   HighsTaskExecutor::shutdown();
+}
+
+TEST_CASE("ParallelCApi", "[parallel]") {
+  // This test exposes a failure in the C api when creating and destroying Highs
+  // instances on separate threads.
+  // One thread solves a mip, while the other loses some time before destroying
+  // the instance. If this causes the scheduler to be terminated (i.e., if
+  // Highs_destroy calls resetGlobalScheduler) while the first thread is still
+  // using it, the first thread may crash, hang, or terminate with wrong
+  // results.
+
+  highs::parallel::initialize_scheduler();
+
+  std::string model = std::string(HIGHS_DIR) + "/check/instances/egout.mps";
+  const double expected_obj = 568.1007;
+  double actual_obj;
+  double total = 0;
+
+  highs::parallel::TaskGroup tg;
+
+  tg.spawn([&]() {
+    void* highs = Highs_create();
+    Highs_setBoolOptionValue(highs, "output_flag", dev_run);
+    Highs_setStringOptionValue(highs, "parallel", "on");
+    Highs_readModel(highs, model.c_str());
+    Highs_run(highs);
+    Highs_getDoubleInfoValue(highs, "objective_function_value", &actual_obj);
+    Highs_destroy(highs);
+  });
+
+  tg.spawn([&]() {
+    void* highs = Highs_create();
+    for (int i = 0; i < 1e6; ++i) {
+      total += (double)i * i * i;
+    }
+    Highs_destroy(highs);
+  });
+
+  tg.taskWait();
+
+  REQUIRE(total > 1e18);
+  REQUIRE(std::abs(actual_obj - expected_obj) / std::abs(expected_obj) < 1e-4);
+
+  HighsTaskExecutor::shutdown(true);
 }