how-to-use-cancellation-to-break-from-a-parallel-loop.md

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Learn more about: How to: Use Cancellation to Break from a Parallel Loop	How to: Use Cancellation to Break from a Parallel Loop	11/04/2016	writing a parallel search algorithm [Concurrency Runtime] parallel search algorithm, writing [Concurrency Runtime]	421cd2de-f058-465f-b890-dd8fcc0df273

How to: Use Cancellation to Break from a Parallel Loop

This example shows how to use cancellation to implement a basic parallel search algorithm.

Example

The following example uses cancellation to search for an element in an array. The parallel_find_any function uses the concurrency::parallel_for algorithm and the concurrency::run_with_cancellation_token function to search for the position that contains the given value. When the parallel loop finds the value, it calls the concurrency::cancellation_token_source::cancel method to cancel future work.

[!code-cppconcrt-parallel-array-search#1]

The concurrency::parallel_for algorithm acts concurrently. Therefore, it does not perform the operations in a pre-determined order. If the array contains multiple instances of the value, the result can be any one of its positions.

Compiling the Code

Copy the example code and paste it in a Visual Studio project, or paste it in a file that is named parallel-array-search.cpp and then run the following command in a Visual Studio Command Prompt window.

cl.exe /EHsc parallel-array-search.cpp

See also

Cancellation in the PPL
Parallel Algorithms
parallel_for Function
cancellation_token_source Class