Invocation concurrency: The number of threads of execution concurrently invoking a service or method.

调用并发性：并发调用服务或方法时执行的线程数。

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The complexity in concurrency programming stems from the fact Threads often needs to operate on the common data. Each Thread has its own sequence of execution, but accesses common data.

并发的复杂性在于，线程需要经常访问共同数据，每个线程都有自己的执行顺序，但需要访问共同数据。

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But getting used to this new model of execution can be a bit awkward, if only because it represents an entirely different way of thinking about concurrency.

但是，习惯这种新的执行模型可能有点儿困难，因为这是一种全新的并发性考虑方式。

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