Archive for March 2014

Lamport, Turing

 

Theories abound (I have my own) about why it did not happen long ago, but at last Lamport did receive the Turing Award. For me what most characterizes him is a stream [1] of elegant, original, insightful articles providing solutions to one important and thorny problem after another. Some of these articles are well known but many gems are not; see for example his take on Buridan’s Ass [2], not even a computer science paper, offering a convincing treatment of a centuries-old riddle.

References

[1] Leslie Lamport: annotated publication list, here.

[2] Leslie Lamport: Buridan’s Principle, “to appear in Foundations of Physics“, dated 24 February 2012, available here.

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New article: contracts in practice

For almost anyone programming in Eiffel, contracts are just a standard part of daily life; Patrice Chalin’s pioneering study of a few years ago [1] confirmed this impression. A larger empirical study is now available to understand how developers actually use contracts when available. The study, to published at FM 2014 [2] covers 21 programs, not just in Eiffel but also in JML and in Code Contracts for C#, totaling 830,000 lines of code, and following the program’s revision history for a grand total of 260 million lines of code over 7700 revisions. It analyzes in detail whether programmers use contracts, how they use them (in particular, which kinds, among preconditions, postconditions and invariants), how contracts evolve over time, and how inheritance interacts with contracts.

The paper is easy to read so I will refer you to it for the detailed conclusions, but one thing is clear: anyone who thinks contracts are for special development or special developers is completely off-track. In an environment supporting contracts, especially as a native part of the language, programmers understand their benefits and apply them as a matter of course.

References

[1] Patrice Chalin: Are practitioners writing contracts?, in Fault-Tolerant System, eds. Butler, Jones, Romanovsky, Troubitsyna, Springer LNCS, vol. 4157, pp. 100–113, 2006.

[2] H.-Christian Estler, Carlo A. Furia, Martin Nordio, Marco Piccioni and Bertrand Meyer: Contracts in Practice, to appear in proceedings of 19th International Symposium on Formal Methods (FM 2014), Singapore, May 2014, draft available here.

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New article: passive processors

 

The SCOOP concurrency model has a clear division of objects into “regions”, improving the clarity and reliability of concurrent programs by establishing a close correspondence between the object structure and the process structure. Each region has an associated “processor”, which executes operations on the region’s objects. A literal application of this rule implies, however, a severe performance penalty. As part of the work for his PhD thesis (defended two weeks ago), Benjamin Morandi found out that a mechanism for specifying certain processors as “passive” yields a considerable performance improvement. The paper, to be published at COORDINATION, describes the technique and its applications.

Reference

Benjamin Morandi, Sebastian Nanz and Bertrand Meyer: Safe and Efficient Data Sharing for Message-Passing Concurrency, to appear in proceedings of COORDINATION 2014, 16th International Conference on Coordination Models and Languages, Berlin, 3-6 June 2014, draft available here.
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Agile book announced

My book “Agile! The Good, the Hype and the Ugly” will be published in a few weeks by Springer. The announced date is April 30 and there is a preview Amazon page: here.

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