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 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;
}