Initialization API

Kokkos::initialize

  Kokkos::initialize();
  Kokkos::initialize(const InitArguments&);
  Kokkos::initialize(int& argc, char* argv[]);

Initializes all enabled Kokkos backends. This function should be called before calling any other Kokkos API functions, including Kokkos object constructors. Kokkos::finalize must be called after Kokkos::initialize.

Kokkos::finalize

  Kokkos::finalize();

Shuts down all enabled Kokkos backends and frees all associated resources. This function should be called after calling all other Kokkos API functions, including Kokkos object destructors. Programs are ill-formed if they do not call this function after calling Kokkos::initialize.

Kokkos::ScopeGuard

ScopeGuard is a class introduced to ensure that Kokkos::initialize and Kokkos::finalize are called correctly even in the presence of unhandled exceptions and multiple libraries trying to "own" Kokkos initialization. ScopeGuard calls Kokkos::initialize in its constructor only if Kokkos::is_initialized() is false, and calls Kokkos::finalize in its destructor only if it called Kokkos::initialize in its constructor.

Kokkos::ScopeGuard::ScopeGuard

  ScopeGuard();
  ScopeGuard(const InitArguments&);
  ScopeGuard(int& argc, char* argv[]);

Calls Kokkos::initialize only if Kokkos::is_initialized() is false. Arguments are passed directly to Kokkos::initialize if it is called.

Kokkos::ScopeGuard::~ScopeGuard

  ~ScopeGuard();

Calls Kokkos::finalize only if the constructor of this object called Kokkos::initialize.

One common mistake is allowing Kokkos objects to live past Kokkos::finalize, which is easy to do since all objects in the scope of main() live past that point. Here is an example of this mistake:

int main(int argc, char** argv) {
  Kokkos::initialize(argc, argv);
  Kokkos::View<double*> my_view("my_view", 10);
  Kokkos::finalize();
  // my_view destructor called after Kokkos::finalize !
}

Switching to Kokkos::ScopeGuard fixes it:

int main(int argc, char** argv) {
  Kokkos::ScopeGuard kokkos(argc, argv);
  Kokkos::View<double*> my_view("my_view", 10);
  // my_view destructor called before Kokkos::finalize
  // ScopeGuard destructor called, calls Kokkos::finalize
}