Towards sound refactoring in erlang

Erlang is an actor-based programming language used extensively for building concurrent, reactive systems that are highly available and suff er minimum downtime. Such systems are often mission critical, making system correctness vital. Refactoring is code restructuring that improves the code but does not change behaviour. While using automated refactoring tools is less error-prone than performing refactorings manually, automated refactoring tools still cannot guarantee that the refactoring is correct, i.e., program behaviour is preserved. This leads to lack of trust in automated refactoring tools. We rst survey solutions to this problem proposed in the literature. Erlang refactoring tools as commonly use approximation techniques which do not guarantee behaviour while some other works propose the use of formal methodologies. In this work we aim to develop a formal methodology for refactoring Erlang code. We study behavioural preorders, with a special focus on the testing preorder as it seems most suited to our purpose.peer-reviewe

On Synchronous and Asynchronous Monitor Instrumentation for Actor-based systems

We study the impact of synchronous and asynchronous monitoring instrumentation on runtime overheads in the context of a runtime verification framework for actor-based systems. We show that, in such a context, asynchronous monitoring incurs substantially lower overhead costs. We also show how, for certain properties that require synchronous monitoring, a hybrid approach can be used that ensures timely violation detections for the important events while, at the same time, incurring lower overhead costs that are closer to those of an asynchronous instrumentation.Comment: In Proceedings FOCLASA 2014, arXiv:1502.0315

A Formal, Resource Consumption-Preserving Translation of Actors to Haskell

We present a formal translation of an actor-based language with cooperative scheduling to the functional language Haskell. The translation is proven correct with respect to a formal semantics of the source language and a high-level operational semantics of the target, i.e. a subset of Haskell. The main correctness theorem is expressed in terms of a simulation relation between the operational semantics of actor programs and their translation. This allows us to then prove that the resource consumption is preserved over this translation, as we establish an equivalence of the cost of the original and Haskell-translated execution traces.Comment: Pre-proceedings paper presented at the 26th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2016), Edinburgh, Scotland UK, 6-8 September 2016 (arXiv:1608.02534

Optimizing Abstract Abstract Machines

The technique of abstracting abstract machines (AAM) provides a systematic approach for deriving computable approximations of evaluators that are easily proved sound. This article contributes a complementary step-by-step process for subsequently going from a naive analyzer derived under the AAM approach, to an efficient and correct implementation. The end result of the process is a two to three order-of-magnitude improvement over the systematically derived analyzer, making it competitive with hand-optimized implementations that compute fundamentally less precise results.Comment: Proceedings of the International Conference on Functional Programming 2013 (ICFP 2013). Boston, Massachusetts. September, 201

Towards Modelling Actor-Based Concurrency in Term Rewriting

In this work, we introduce a scheme for modelling actor systems within sequential term rewriting. In our proposal, a TRS consists of the union of three components: the functional part (which is specific of a system), a set of rules for reducing concurrent actions, and a set of rules for defining a particular scheduling policy. A key ingredient of our approach is that concurrent systems are modelled by terms in which concurrent actions can never occur inside user-defined function calls. This assumption greatly simplifies the definition of the semantics for concurrent actions, since no term traversal will be needed. We prove that these systems are well defined in the sense that concurrent actions can always be reduced. Our approach can be used as a basis for modelling actor-based concurrent programs, which can then be analyzed using existing techniques for term rewrite systems

Towards Symbolic Execution in Erlang

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-662-46823-4_28The concurrent functional language Erlang [1] has a number of distinguishing features, like dynamic typing, concurrency via asynchronous message passing or hot code loading, that make it especially appropriate for distributed, faulttolerant, soft real-time applications. The success of Erlang is witnessed by the increasing number of its industrial applications. For instance, Erlang has been used to implement Facebook’s chat back-end, the mobile application Whatsapp or Twitterfall—a service to view trends and patterns from Twitter—, to name a few. The success of the language, however, also requires the development of powerful testing and verification techniques. Symbolic execution is at the core of many program analysis and transformation techniques, like partial evaluation, test-case generation or model checking. In this paper, we introduce a symbolic execution technique for Erlang. We discuss how both an overapproximation and an underapproximation of the concrete semantics can be obtained. We illustrate our approach through some examples. To the best of our knowledge, this is the first attempt to formalize symbolic execution in the context of this language, where previous approaches have only considered exploring different schedulings but have not dealt with symbolic data. More details can be found in the companion technical reportThis work has been partially supported by the Spanish Ministerio de Economía y Competitividad (Secretaría de Estado de Investigación, Desarrollo e Innovación) under grant TIN2013-44742-C4-1-R and by the Generalitat Valenciana under grant PROMETEO/2011/052.Vidal Oriola, GF. (2015). Towards Symbolic Execution in Erlang. En Perspectives of System Informatics. Springer. 351-360. https://doi.org/10.1007/978-3-662-46823-4_28S35136