Modern concurrency abstractions for C#

Reviewer: Sergei Gorlatch

Polyphonic C#, an extension of the C# language, is presented in this paper. It is based on the join calculus, and seeks to facilitate the development of concurrent programs. The main new features are asynchronous methods, and so-called chords. Asynchronous methods in Polyphonic C# return immediately, and do not return a value (but they may have parameters). A chord is essentially a list of methods (the header) and a chord body. The body is only executed when all of the methods of the chord have been called. The chord header contains exactly one synchronous, and any number of asynchronous, methods. The return value of the synchronous method is computed in the chord body, probably using parameters passed to one of the asynchronous methods. This paper presents a detailed informal specification of the Polyphonic C# language extensions, and provides a few small but interesting examples of the use of chords and asynchronous methods. The authors describe the implementation in C#, and compare the performance of Polyphonic C# with standard C#. The paper concludes with a presentation of related work, and hints at future improvements. In general, the paper is interesting to read, although the information provided is often quite specific to C#, and will thus be of interest mostly to readers familiar with the C# language. Unfortunately, there is no language-independent introduction to the join calculus; instead, only the Polyphonic C# implementation is described. However, the examples provided in the paper (single cell buffer, reader-writer locks, active objects, and a few others) are very interesting to read, and provide a good impression of the expressive power of chords. The section covering the Polyphonic C# implementation goes into great detail about the implementation. Though the presentation may be quite interesting for C# programmers, a reader with only a general interest in concurrent programming may find it somewhat lengthy. In summary, the paper presents the integration of asynchronous methods and chords into the C# framework, and will definitively be very interesting for anybody concerned with C#, but will also be of interest to readers with only a general concern for concurrent programming. Online Computing Reviews Service