Automatic autoprojection of recursive equations with global variables and abstract data types

AbstractSelf-applicable partial evaluation has been implemented for half a decade now, but many problems remain open. This paper addresses and solves the problems of automating call unfolding, having an open-ended set of operators, and processing global variables updated by side effects. The problems of computation duplication and termination of residual programs are addressed and solved: residual programs never duplicate computations of the source program; residual programs do not terminate more often than source programs.This paper describes the automatic autoprojector (self-applicable partial evaluator) Similix; it handles programs with user-defined primitive abstract data type operators which may process global variables. Abstract data types make it possible to hide actual representations of data and prevent specializing operators over these representations. The formally sound treatment of global variables makes Similix fit well in an applicative order programming environment.We present a new method for automatic call unfolding which is simpler, faster, and sometimes more effective than existing methods: it requires neither recursion analysis of the source program, nor call graph analysis of the residual program.To avoid duplicating computations and preserve termination properties, we introduce an abstract interpretation of the source program, abstract occurence counting analysis, which is performed during preprocessing. We express it formally and simplify it

On Grainless Footprint Semantics for Shared-memory Programs

AbstractWe develop an improved grainless denotational semantics for shared-memory parallel programs, building on ideas from earlier trace-based models with local states and footprints [S. Brookes. A Grainless Semantics for Parallel Programs with Shared Mutable State. Proc. 21st Conference on Mathematical Foundations of Programming Semantics (MFPS XXI). Birmingham, 17–21 May, 2005]. The key new idea is a more refined approach to race detection, leading to a model with better abstraction properties. Rather than treat a race condition as a “global” catastrophe [S. Brookes. A Semantics for Concurrent Separation Logic. Invited paper, CONCUR 2004, Philippa Gardner and Nobuko Yoshida (Eds.), Springer LNCS 3170, London, August/September 2004, pp. 16–34; S. Brookes. A Grainless Semantics for Parallel Programs with Shared Mutable State. Proc. 21st Conference on Mathematical Foundations of Programming Semantics (MFPS XXI). Birmingham, 17–21 May, 2005], we track information about variables whose value may be tainted by a race, and retain accurate information about unaffected variables. As in the prior work, we abstract away from state changes that occur in between synchronization points, in a manner consistent with Dijkstra's Principle [E. W. Dijkstra. Cooperating sequential processes. In: Programming Languages, F. Genuys (editor), pp. 43–112. Academic Press, 1968]. We obtain a model in which only synchronization operations (for locking and unlocking binary semaphores) are deemed to be atomic, which matches the usual implementation of these constructs in an abstract manner. Apart from this, no other atomicity assumptions are made, so our model is truly grainless. Our semantics supports compositional program analysis based on “sequential” reasoning for sequential code fragments, even when this code occurs in parallel contexts, and yields a simple semantic characterization of race-free code. The semantics validates the static constraints on “critical variables” imposed in concurrent programming methodology [C.A.R. Hoare. Towards a Theory of Parallel Programming. In Operating Systems Techniques, C.A.R. Hoare and R.H. Perrott, editors, pp. 61–71, Academic Press, 1972; S. Owicki and D. Gries. Verifying properties of parallel programs: An axiomatic approach, Comm. ACM. 19(5):279–285, May 1976] and serves as a foundation for reasoning about safe partial correctness, as in concurrent separation logic [P.W. O'Hearn. Resources, Concurrency, and Local Reasoning. Invited paper, CONCUR 2004, Philippa Gardner and Nobuko Yoshida (Eds.), Springer LNCS 3170, London, August/September 2004, pp. 49–67]. The new treatment of race detection allows for more refined analysis of racy programs. By framing our ideas and concepts in a general manner we hope that our results may be applied in a wider setting

A new module system for prolog

It is now widely accepted that separating programs into modules has proven very useful in program development and maintenance. While many Prolog implementations include useful module systems, we feel that these systems can be improved in a number of ways, such as, for example, being more amenable to effective global analysis and allowing sepárate compilation or sensible creation of standalone executables. We discuss a number of issues related to the design of such an improved module system for Prolog. Based on this, we present the choices made in the Ciao module system, which has been designed to meet a number of objectives: allowing sepárate compilation, extensibility in features and in syntax, amenability to modular global analysis, etc

Proceedings of International Workshop "Global Computing: Programming Environments, Languages, Security and Analysis of Systems"

According to the IST/ FET proactive initiative on GLOBAL COMPUTING, the goal is to obtain techniques (models, frameworks, methods, algorithms) for constructing systems that are flexible, dependable, secure, robust and efficient. The dominant concerns are not those of representing and manipulating data efficiently but rather those of handling the co-ordination and interaction, security, reliability, robustness, failure modes, and control of risk of the entities in the system and the overall design, description and performance of the system itself. Completely different paradigms of computer science may have to be developed to tackle these issues effectively. The research should concentrate on systems having the following characteristics: • The systems are composed of autonomous computational entities where activity is not centrally controlled, either because global control is impossible or impractical, or because the entities are created or controlled by different owners. • The computational entities are mobile, due to the movement of the physical platforms or by movement of the entity from one platform to another. • The configuration varies over time. For instance, the system is open to the introduction of new computational entities and likewise their deletion. The behaviour of the entities may vary over time. • The systems operate with incomplete information about the environment. For instance, information becomes rapidly out of date and mobility requires information about the environment to be discovered. The ultimate goal of the research action is to provide a solid scientific foundation for the design of such systems, and to lay the groundwork for achieving effective principles for building and analysing such systems. This workshop covers the aspects related to languages and programming environments as well as analysis of systems and resources involving 9 projects (AGILE , DART, DEGAS , MIKADO, MRG, MYTHS, PEPITO, PROFUNDIS, SECURE) out of the 13 founded under the initiative. After an year from the start of the projects, the goal of the workshop is to fix the state of the art on the topics covered by the two clusters related to programming environments and analysis of systems as well as to devise strategies and new ideas to profitably continue the research effort towards the overall objective of the initiative. We acknowledge the Dipartimento di Informatica and Tlc of the University of Trento, the Comune di Rovereto, the project DEGAS for partially funding the event and the Events and Meetings Office of the University of Trento for the valuable collaboration