add_mp_perf_env Subroutine

   SUBROUTINE add_mp_perf_env(perf_env)
      !! start and stop the performance indicators
      !! for every call to start there has to be (exactly) one call to stop
      !! @note
      !! can be used to measure performance of a sub-part of a program.
      !! timings measured here will not show up in the outer start/stops
      !! Doesn't need a fresh communicator

      TYPE(mp_perf_env_type), OPTIONAL, POINTER          :: perf_env

      stack_pointer = stack_pointer + 1
      IF (stack_pointer > max_stack_size) THEN
         DBCSR_ABORT("stack_pointer too large : mpiwrap @ add_mp_perf_env")
      END IF
      NULLIFY (mp_perf_stack(stack_pointer)%mp_perf_env)
      IF (PRESENT(perf_env)) THEN
         mp_perf_stack(stack_pointer)%mp_perf_env => perf_env
         IF (ASSOCIATED(perf_env)) CALL mp_perf_env_retain(perf_env)
      END IF
      IF (.NOT. ASSOCIATED(mp_perf_stack(stack_pointer)%mp_perf_env)) THEN
         CALL mp_perf_env_create(mp_perf_stack(stack_pointer)%mp_perf_env)
      END IF
   END SUBROUTINE add_mp_perf_env