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Task cancellation in VS2010 version RRS feed

  • Question

  • First I would like to express my thanks to the team for making PPL tasks available for those of us who must stick with VS2010 C++ compiler for a while.

    They work great for me so far.

    One minor detail: this code below wouldn't compile because interruption_point and is_task_cancellation_requested functions could not be found:

    void PrintStuff()
    {
       while(true)
       {
          //interruption_point();
          //if(is_task_cancellation_requested())
          //{
          //   cancel_current_task();
          //}
          std::cout << '.';
       }
    
       std::cout << std::endl;
    }

    I am able to work  around these issues by passing cancellation token as a parameter to function. I wonder if I am missing something, or are these functions indeed not implemented, for whatever reason?

    In fact, I am not sure that I understand how to create a cancellable task, short of creating an external cancellation token and capturing it in task's lambda.

     

    • Edited by Tonko Saturday, November 24, 2012 6:47 PM
    Saturday, November 24, 2012 6:44 PM

Answers

  • Tonko,

    Thanks for the kind words!

    The pplx namespace that you see in Casablanca is the beginning of our effort to make PPL platform- and compiler-independent. For now, we ported just enough of the PPL to support asynchronous operations for Casablanca, but not the parts of the PPL that rely on the task_group class, such as the parallel_for and other parallel algorithms.

    The APIs you mentioned are useful when combining PPL tasks with the task_group-based parallel algorithms that do not support cancellation tokens.

    If you only use PPL tasks and not other PPL algorithms, cancellation tokens is a great way to go. We like them for their explicitness - cancellation tokens make it very clear how the cancellation is requested, how it's propagated to other tasks, and what tasks react to them.

    So what you call a work around is actually a perfectly fine way of doing it!


    Artur Laksberg Visual C++ Team Microsoft

    • Marked as answer by Tonko Monday, November 26, 2012 10:54 PM
    Monday, November 26, 2012 8:22 PM