Provides access to the element at the given index in the concurrent vector. This method is concurrency-safe for read operations, and also while growing the vector, as long as you have ensured that the value _Index is less than the size of the concurrent vector.
The version of the function at that returns a non-const refernce cannot be used to concurrently write to the element from different threads. A different synchronization object should be used to synchronize concurrent read and write operations to the same data element.
The method throws out_of_range if _Index is greater than or equal to the size of the concurrent vector, and range_error if the index is for a broken portion of the vector. For details on how a vector can become broken, see Parallel Containers and Objects.