JFLP: Volume 1997, Article 6

The Journal of Functional and Logic Programming

Volume 1997

Article 6

Published by The MIT Press . Copyright 1997 Massachusetts Institute of Technology.


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Abstracting Synchronization in Concurrent Constraint Programming

Enea Zaffanella, Roberto Giacobazzi , and Giorgio Levi

5 November 1997


Because of synchronization based on blocking ask , some of the most important techniques for data-flow analysis of (sequential) constraint logic programs ( clp ) are no longer applicable to cc languages. In particular, the generalized approach to the semantics, intended to factorize the (standard) semantics so as to make explicit the domain-dependent features (i.e., operators and semantic objects that may be influenced by abstraction) becomes useless for relevant applications. In the case of clp programs, abstract interpretation of a program P is obtained by evaluating an abstract program $\alpha(P)$ into an instance of clp itself, provided with a suitable abstract constraint system. In cc programs, a correct characterization of suspended computations can only be obtained by replacing ask constraints with stronger constraints, which is not the case in abstract interpretation, where abstraction is usually a weakening of constraints. A possible solution to this problem is based on a more abstract (nonstandard) semantics: the success semantics, which models nonsuspended computations only. With a program transformation (NoSynch) that simply ignores synchronization, we obtain a clp like program that allows us to apply standard techniques for data-flow analysis. For suspension-free programs, the success semantics is equivalent to the standard semantics, thus justifying the use of suspension analysis to generate sound approximations. A second transformation ( Angel ) is introduced, applying a different abstraction of synchronization in possibly suspending programs. The resulting abstraction is adequate to suspension analysis. Applicability and accuracy of these solutions are investigated.
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Self citation

      author={Enea Zaffanella, Roberto Giacobazzi, and Giorgio Levi},
      title={Abstracting Synchronization in Concurrent Constraint Programming},
      journal={Journal of Functional and Logic Programming},
      publisher={The MIT Press},


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