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multi-core and parallel programming: is the sky falling?

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The CCC blog has published a couple of articles on the multi-core challenge, all emphasizing the difficulty of making parallel programming prevalent and, hence, the difficulty of leveraging multi-core systems in mass markets. The challenge is, indeed, significant and requires important investments in research and development; but, at UPCRC Illinois , we do not believe that the sky is falling.

Parallel programming, as currently practiced, is hard: Programs, especially shared memory programs, are prone to subtle, hard-to-find synchronization bugs and parallel performance is elusive. One can reach two possible conclusions from this situation: It is possible that parallel programming is inherently hard, in which case, indeed the sky is falling. An alternative view is that, intrinsically, parallel programming is not significantly harder than sequential programming; rather, it is hampered by the lack of adequate languages, tools and architectures.  In this alternative view, different practices, supported by the right infrastructure, can make parallel programming prevalent.

This alternative, optimistic view is based on many years of experience with parallel programming. While some concurrent code, e.g., OS code, is often hard to write and debug, there are many forms of parallelism that are relatively easy to master: Many parallel scientific codes are written by scientists with limited CS education; the time spent handling parallelism is a small fraction of the time spent developing a large parallel scientific code. Parallelism can be hidden behind an SQL interface and exploited by programmers with little difficulty. Many programmers develop GUI’s that are, in effect, parallel programs, using specialized frameworks. Parallelism can be exposed using scripted object systems such as Squeak Etoys in ways that enable young children to write parallel programs. These examples seem to indicate that it is not parallelism per se that is hard to handle; rather it is the unstructured, unconstrained interaction between concurrent threads that result in code that is hard to understand both from a correctness and performance view, hence hard to debug and tune.

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