Question

I’m currently writing a large multi threaded C++ program (> 50K LOC).

As such I’ve been motivated to read up alot on various techniques for handling multi-threaded code. One theory I’ve found to be quite cool is:

http://en.wikipedia.org/wiki/Communicating_sequential_processes

And it’s invented by a slightly famous guy, who’s made other non-trivial contributions to concurrent programming.

However, is CSP used in practice? Can anyone point to any large application written in a CSP style?

Thanks!

Answer 1

CSP, as a process calculus, is fundamentally a theoretical thing that enables us to formalize and study some aspects of a parallel program.

If you instead want a theory that enables you to build distributed programs, then you should take a look to parallel structured programming.

Parallel structural programming is the base of the current HPC (high-performance computing) research and provides to you a methodology about how to approach and design parallel programs (essentially, flowcharts of communicating computing nodes) and runtime systems to implements them.

A central idea in parallel structured programming is that of algorithmic skeleton, developed initially by Murray Cole. A skeleton is a thing like a parallel design pattern with a cost model associated and (usually) a run-time system that supports it. A skeleton models, study and supports a class of parallel algorithms that have a certain “shape”.

As a notable example, mapreduce (made popular by Google) is just a kind of skeleton that address data parallelism, where a computation can be described by a map phase (apply a function f to all elements that compose the input data), and a reduce phase (take all the transformed items and “combine” them using an associative operator +).

I found the idea of parallel structured programming both theoretical sound and practical useful, so I’ll suggest to give a look to it.

A word about multi-threading: since skeletons addresses massive parallelism, usually they are implemented in distributed memory instead of shared. Intel has developed a tool, TBB, which address multi-threading and (partially) follows the parallel structured programming framework. It is a C++ library, so probably you can just start using it in your projects.