There exists an extension to C called Unified Parallel C (UPC) designed for large-scale parallel computation. It actually has a upc_forall command. According to the specs, using that command signals to the compiler to use threads, similar to the last slide.

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Thanks for the clarification. But is this forall command equivalent to the last page with the pthread? Do we also use the same synchronization methods if there's any shared state that needs protecting?

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@lixf This slide and the previous slide is saying that either the programmer explicitly adds parallelism, or the programmer marks a computation as parallel. Then the compiler can do what it can with that information. Most obvious choice for the compiler here is to add in pthreads, just like in the previous slide. But the compiler might not do anything at all! It could just ignore the forall and compile it as if it was a sequential for loop.

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It seems appropriate, given @jinsikl's comment, to therefore draw attention to how this shows us the difference between abstraction and implementation. We can choose, as the programmer, to adopt existing frameworks which have abstract commands like forall and not be concerned about the underlying implementation or we could write the full thing ourselves.

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