Set maximum number of threads to 8 for unit tests

tests/mpi_test_main.cpp

@@ -28,7 +28,7 @@ main(int argc, char* argv[])
   parallel::Messenger::create(argc, argv);
 
   const int nb_max_threads = std::max(std::thread::hardware_concurrency(), 1u);
-  int nb_threads           = std::max(nb_max_threads / parallel::Messenger::getInstance().size(), 1ul);
+  int nb_threads           = std::min(std::max(nb_max_threads / parallel::Messenger::getInstance().size(), 1ul), 8ul);
 
   Catch::Session session;
 

tests/test_main.cpp

@@ -23,7 +23,7 @@ int
 main(int argc, char* argv[])
 {
   parallel::Messenger::create(argc, argv);
-  int nb_threads = std::max(std::thread::hardware_concurrency() / 2, 1u);
+  int nb_threads = std::min(std::max(std::thread::hardware_concurrency() / 2, 1u), 8u);
 
   Catch::Session session;