2,076 research outputs found
Formal Derivation of Concurrent Garbage Collectors
Concurrent garbage collectors are notoriously difficult to implement
correctly. Previous approaches to the issue of producing correct collectors
have mainly been based on posit-and-prove verification or on the application of
domain-specific templates and transformations. We show how to derive the upper
reaches of a family of concurrent garbage collectors by refinement from a
formal specification, emphasizing the application of domain-independent design
theories and transformations. A key contribution is an extension to the
classical lattice-theoretic fixpoint theorems to account for the dynamics of
concurrent mutation and collection.Comment: 38 pages, 21 figures. The short version of this paper appeared in the
Proceedings of MPC 201
Cogent: uniqueness types and certifying compilation
This paper presents a framework aimed at significantly reducing the cost of proving functional correctness for low-level operating systems components. The framework is designed around a new functional programming language, Cogent. A central aspect of the language is its uniqueness type system, which eliminates the need for a trusted runtime or garbage collector while still guaranteeing memory safety, a crucial property for safety and security. Moreover, it allows us to assign two semantics to the language: The first semantics is imperative, suitable for efficient C code generation, and the second is purely functional, providing a user-friendly interface for equational reasoning and verification of higher-level correctness properties. The refinement theorem connecting the two semantics allows the compiler to produce a proof via translation validation certifying the correctness of the generated C code with respect to the semantics of the Cogent source program. We have demonstrated the effectiveness of our framework for implementation and for verification through two file system implementations
Garbage collection in distributed systems
PhD ThesisThe provision of system-wide heap storage has a number of advantages.
However, when the technique is applied to distributed systems
automatically recovering inaccessible variables becomes a serious problem.
This thesis presents a survey of such garbage collection techniques but
finds that no existing algorithm is entirely suitable. A new, general
purpose algorithm is developed and presented which allows individual
systems to garbage collect largely independently. The effects of these
garbage collections are combined, using recursively structured control
mechanisms, to achieve garbage collection of the entire heap with the
minimum of overheads. Experimental results show that new algorithm
recovers most inaccessible variables more quickly than a straightforward
garbage collection, giving an improved memory utilisation
Conference Series
Civl is a static verifier for concurrent programs designed around the conceptual framework of layered refinement,
which views the task of verifying a program as a sequence of program simplification steps each justified by its own invariant. Civl verifies a layered concurrent program that compactly expresses all the programs in this sequence and the supporting invariants. This paper presents the design and implementation of the Civl verifier
Implementing and reasoning about hash-consed data structures in Coq
We report on four different approaches to implementing hash-consing in Coq
programs. The use cases include execution inside Coq, or execution of the
extracted OCaml code. We explore the different trade-offs between faithful use
of pristine extracted code, and code that is fine-tuned to make use of OCaml
programming constructs not available in Coq. We discuss the possible
consequences in terms of performances and guarantees. We use the running
example of binary decision diagrams and then demonstrate the generality of our
solutions by applying them to other examples of hash-consed data structures
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