.. _Cancellation_Without_An_Exception: Cancellation Without An Exception ================================= To cancel an algorithm but not throw an exception, use the expression ``current_context()->cancel_group_execution()``. The part ``current_context()`` references the ``task_group_context*`` of the currently executing task if any on the current thread. Calling ``cancel_group_execution()`` cancels all tasks in its ``task_group_context``, which is explained in more detail in :ref:`Cancellation_and_Nested_Parallelism`. The method returns ``true`` if it actually causes cancellation, ``false`` if the ``task_group_context`` was already cancelled. The example below shows how to use ``current_context()->cancel_group_execution()``. :: #include "oneapi/tbb.h" #include <vector> #include <iostream> using namespace oneapi::tbb; using namespace std; vector<int> Data; struct Update { void operator()( const blocked_range<int>& r ) const { for( int i=r.begin(); i!=r.end(); ++i ) if( i<Data.size() ) { ++Data[i]; } else { // Cancel related tasks. if( current_context()->cancel_group_execution() ) cout << "Index " << i << " caused cancellation\n"; return; } } }; int main() { Data.resize(1000); parallel_for( blocked_range<int>(0, 2000), Update()); return 0; }
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