text: /*
      Copyright (c) 2005-2019 Intel Corporation
  
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
  
          http://www.apache.org/licenses/LICENSE-2.0
  
      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.
  */
  
  #ifndef __TBB_task_scheduler_init_H
  #define __TBB_task_scheduler_init_H
  
  #include "tbb_stddef.h"
  #include "limits.h"
  #if __TBB_SUPPORTS_WORKERS_WAITING_IN_TERMINATE
  #include <new> // nothrow_t
  #endif
  
  namespace tbb {
  
  typedef std::size_t stack_size_type;
  
  //! @cond INTERNAL
  namespace internal {
      //! Internal to library. Should not be used by clients.
      /** @ingroup task_scheduling */
      class scheduler;
  } // namespace internal
  //! @endcond
  
  //! Class delimiting the scope of task scheduler activity.
  /** A thread can construct a task_scheduler_init object and keep it alive
      while it uses TBB's tasking subsystem (including parallel algorithms).
  
      This class allows to customize properties of the TBB task pool to some extent.
      For example it can limit concurrency level of parallel work initiated by the
      given thread. It also can be used to specify stack size of the TBB worker threads,
      though this setting is not effective if the thread pool has already been created.
  
      If a parallel construct is used without task_scheduler_init object previously
      created, the scheduler will be initialized automatically with default settings,
      and will persist until this thread exits. Default concurrency level is defined
      as described in task_scheduler_init::initialize().
      @ingroup task_scheduling */
  class task_scheduler_init: internal::no_copy {
      enum ExceptionPropagationMode {
          propagation_mode_exact = 1u,
          propagation_mode_captured = 2u,
          propagation_mode_mask = propagation_mode_exact | propagation_mode_captured
      };
  
      /** NULL if not currently initialized. */
      internal::scheduler* my_scheduler;
  
      bool internal_terminate( bool blocking );
  #if __TBB_SUPPORTS_WORKERS_WAITING_IN_TERMINATE
      bool __TBB_EXPORTED_METHOD internal_blocking_terminate( bool throwing );
  #endif
  public:
  
      //! Typedef for number of threads that is automatic.
      static const int automatic = -1;
  
      //! Argument to initialize() or constructor that causes initialization to be deferred.
      static const int deferred = -2;
  
      //! Ensure that scheduler exists for this thread
      /** A value of -1 lets TBB decide on the number of threads, which is usually
          maximal hardware concurrency for this process, that is the number of logical
          CPUs on the machine (possibly limited by the processor affinity mask of this
          process (Windows) or of this thread (Linux, FreeBSD). It is preferable option
          for production code because it helps to avoid nasty surprises when several
          TBB based components run side-by-side or in a nested fashion inside the same
          process.
  
          The number_of_threads is ignored if any other task_scheduler_inits
          currently exist.  A thread may construct multiple task_scheduler_inits.
          Doing so does no harm because the underlying scheduler is reference counted. */
      void __TBB_EXPORTED_METHOD initialize( int number_of_threads=automatic );
  
      //! The overloaded method with stack size parameter
      /** Overloading is necessary to preserve ABI compatibility */
      void __TBB_EXPORTED_METHOD initialize( int number_of_threads, stack_size_type thread_stack_size );
  
      //! Inverse of method initialize.
      void __TBB_EXPORTED_METHOD terminate();
  
  #if __TBB_SUPPORTS_WORKERS_WAITING_IN_TERMINATE
  #if TBB_USE_EXCEPTIONS
      //! terminate() that waits for worker threads termination. Throws exception on error.
      void blocking_terminate() {
          internal_blocking_terminate( /*throwing=*/true );
      }
  #endif
      //! terminate() that waits for worker threads termination. Returns false on error.
      bool blocking_terminate(const std::nothrow_t&) __TBB_NOEXCEPT(true) {
          return internal_blocking_terminate( /*throwing=*/false );
      }
  #endif // __TBB_SUPPORTS_WORKERS_WAITING_IN_TERMINATE
  
      //! Shorthand for default constructor followed by call to initialize(number_of_threads).
      task_scheduler_init( int number_of_threads=automatic, stack_size_type thread_stack_size=0 ) : my_scheduler(NULL)
      {
          // Two lowest order bits of the stack size argument may be taken to communicate
          // default exception propagation mode of the client to be used when the
          // client manually creates tasks in the master thread and does not use
          // explicit task group context object. This is necessary because newer
          // TBB binaries with exact propagation enabled by default may be used
          // by older clients that expect tbb::captured_exception wrapper.
          // All zeros mean old client - no preference.
          __TBB_ASSERT( !(thread_stack_size & propagation_mode_mask), "Requested stack size is not aligned" );
  #if TBB_USE_EXCEPTIONS
          thread_stack_size |= TBB_USE_CAPTURED_EXCEPTION ? propagation_mode_captured : propagation_mode_exact;
  #endif /* TBB_USE_EXCEPTIONS */
          initialize( number_of_threads, thread_stack_size );
      }
  
      //! Destroy scheduler for this thread if thread has no other live task_scheduler_inits.
      ~task_scheduler_init() {
          if( my_scheduler )
              terminate();
          internal::poison_pointer( my_scheduler );
      }
      //! Returns the number of threads TBB scheduler would create if initialized by default.
      /** Result returned by this method does not depend on whether the scheduler
          has already been initialized.
  
          Because tbb 2.0 does not support blocking tasks yet, you may use this method
          to boost the number of threads in the tbb's internal pool, if your tasks are
          doing I/O operations. The optimal number of additional threads depends on how
          much time your tasks spend in the blocked state.
  
          Before TBB 3.0 U4 this method returned the number of logical CPU in the
          system. Currently on Windows, Linux and FreeBSD it returns the number of
          logical CPUs available to the current process in accordance with its affinity
          mask.
  
          NOTE: The return value of this method never changes after its first invocation.
          This means that changes in the process affinity mask that took place after
          this method was first invoked will not affect the number of worker threads
          in the TBB worker threads pool. */
      static int __TBB_EXPORTED_FUNC default_num_threads ();
  
      //! Returns true if scheduler is active (initialized); false otherwise
      bool is_active() const { return my_scheduler != NULL; }
  };
  
  } // namespace tbb
  
  #endif /* __TBB_task_scheduler_init_H */
  