`is_initialized` and `is_finalized`¶

Defined in header <Kokkos_Core.hpp>

Usage¶

if(Kokkos::is_initialized()) {
  // do work
}
if(!Kokkos::is_initialized() && Kokkos::is_finalized()) {
  // may initialize Kokkos
}

The functions is_initialized() and is_finalized() allow applications to query the current state of the Kokkos execution environment. Because Kokkos follows a strict linear lifecycle, these functions are often used to ensure that initialization or finalization occurs exactly once.

Interface¶

bool is_initialized() noexcept¶

Returns:: true if the Kokkos execution environment is currently active and usable.

bool is_finalized() noexcept¶

Returns:: true if the Kokkos execution environment has been shut down via finalize().

Notes¶

Note

The Lifecycle State Machine

Kokkos moves through three distinct states. Note that once Kokkos is finalized, it cannot be re-initialized within the same process execution.

Program Phase	`is_initialized()`	`is_finalized()`	Description
Pre-Initialization	`false`	`false`	Kokkos is not yet active.
Active	`true`	`false`	`initialize()` has been called. Kernels can be launched.
Post-Finalization	`false`	`true`	`finalize()` has been called. Kokkos is no longer usable.

Caution

Comparison with MPI: Users familiar with MPI should note a key difference. In MPI, MPI_Initialized returns true even after MPI_Finalize is called. In Kokkos, is_initialized() returns false after finalization.

To check if Kokkos::initialize() was ever called, use the logic:

if (Kokkos::is_initialized() || Kokkos::is_finalized()) { ... }

Example¶

#include <Kokkos_Core.hpp>
#include <cstdio>

int main(int argc, char* argv[]) {
  printf("before initialize: initialized=%d finalized=%d\n",
    Kokkos::is_initialized(), Kokkos::is_finalized());

  Kokkos::initialize();

  printf("kokkos active:     initialized=%d finalized=%d\n",
    Kokkos::is_initialized(), Kokkos::is_finalized());

  Kokkos::finalize();

  printf("after finalize:    initialized=%d finalized=%d\n",
    Kokkos::is_initialized(), Kokkos::is_finalized());
}

Output:

before initialize: initialized=0 finalized=0
kokkos active:     initialized=1 finalized=0
after finalize:    initialized=0 finalized=1