Automatic Distributed Code Generation from Formal Models of Asynchronous Concurrent Processes

International audienceFormal process languages inheriting the concurrency and communication features of process algebras are convenient formalisms to model distributed applications, especially when they are equipped with formal verification tools (e.g., model-checkers) to help hunting for bugs early in the development process. However, even starting from a fully verified formal model, bugs are likely to be introduced while translating (generally by hand) the concurrent model —which relies on high-level and expressive communication primitives— into the distributed implementation —which often relies on low-level communication primitives. In this paper, we present DLC, a compiler that enables distributed code to be generated from models written in a formal process language called LNT, which is equipped with a rich verification toolbox named CADP. The generated code can be either executed in an autonomous way (i.e., without requiring additional code to be defined by the user), or connected to external software through user-modifiable C functions. We present an experiment where DLC generates a distributed implementation from the LNT model of the Raft consensus algorithm

CFSIM: A concurrent compiled-code functional simulator for hopCP

Journal ArticleControl intensive ICs pose a significant challenge to the users of formal methods in designing hardware. These ICs have to support a wide variety of requirements including synchronous and asynchronous operations, polling and interrupt-driven modes of operation, multiple concurrent threads of execution, complex computations, and programmability. In this paper, we illustrate the use of formal methods in the design of a control intensive IC called the "Intel 8251" Universal Synchronous/Asynchronous Receiver/Transmitter (USART), using our formal hardware description language 'hopCP'. A feature of hopCP is that it supports communication via asynchronous ports (distributed shared variables writable by exactly one process), in addition to synchronous message passing. We show the usefulness of this combination of communication constructs. We outline static analysis algorithms to determine safe usages of asynchronous ports, and also to discover other static properties of the specification. We discuss a compiled-code concurrent functional simulator called CFSIM, as well as the use of concurrent testers for driving CFSIM. The use of a semantically well specified and simple language, and the associated analysis/simulation tools helps conquer the complexity of specifying and validating control intensive ICs

Specification and validation of control intensive ICs in hopCP

technical reportControl intensive ICs pose a significant challenge to the users of formal methods in designing hardware. These ICs have to support a wide variety of requirements including synchronous and asynchronous operations polling and interrupt driven modes of operation multiple concurrent threads of execution non-trivial computational requirements and programmability. In this paper we illustrate the use of formal methods in the design of a control intensive IC called the "Intel 8251" Universal Synchronous / Asynchronous Receiver Transmitter (USART), using our hardware description language 'hopCP'. A feature of hopCP is that it supports communication via synchronous ports in addition to synchronous message passing Asynchronous ports are distributed shared variables writable by exactly one process We show the usefulness of this combination of communication constructs We outline algorithms to determine safe usages of asynchronous ports and also to discover other static properties of the specification We discuss a compiled code concurrent functional simulator called CFSIM, as well as the use of concurrent testers for driving CFSIM. The use of a semantically well specified and simple language and the associated analysis/simulation tools helps conquer the complexity of specifying and validating control intensive ICs

Mobile support in CSCW applications and groupware development frameworks

Computer Supported Cooperative Work (CSCW) is an established subset of the field of Human Computer Interaction that deals with the how people use computing technology to enhance group interaction and collaboration. Mobile CSCW has emerged as a result of the progression from personal desktop computing to the mobile device platforms that are ubiquitous today. CSCW aims to not only connect people and facilitate communication through using computers; it aims to provide conceptual models coupled with technology to manage, mediate, and assist collaborative processes. Mobile CSCW research looks to fulfil these aims through the adoption of mobile technology and consideration for the mobile user. Facilitating collaboration using mobile devices brings new challenges. Some of these challenges are inherent to the nature of the device hardware, while others focus on the understanding of how to engineer software to maximize effectiveness for the end-users. This paper reviews seminal and state-of-the-art cooperative software applications and development frameworks, and their support for mobile devices

Specification and validation of control-intensive integrated circuits in hopCP

technical reportControl intensive ICs pose a significant challenge to the users of formal methods in designing hardware. These ICs have to support a wide variety of requirements including synchronous and asynchronous operations, polling and interrupt-driven modes of operation, multiple concurrent threads of execution, complex computations, and programmability. In this paper, we illustrate the use of formal methods in the design of a control intensive IC called the "Intel 8251" Universal Synchronous/Asynchronous Receiver/Transmitter (USART), using our formal hardware description language 'hopCP'. A feature of hopCP is that it supports communication via asynchronous ports (distributed shared variables writable by exactly one process), in addition to synchronous message passing. We show the usefulness of this combination of communication constructs. We outline static analysis algorithms to determine safe usages of asynchronous ports, and also to discover other static properties of the specification. We discuss a compiled-code concurrent functional simulator called CFSIM, as well as the use of concurrent testers for driving CFSIM. The use of a seraantically well specified and simple language, and the associated analysis/simulation tools helps conquer the complexity of specifying and validating control intensive ICs

Systematic composition of distributed objects: Processes and sessions

We consider a system with the infrastructure for the creation and interconnection of large numbers of distributed persistent objects. This system is exemplified by the Internet: potentially, every appliance and document on the Internet has both persistent state and the ability to interact with large numbers of other appliances and documents on the Internet. This paper elucidates the characteristics of such a system, and proposes the compositional requirements of its corresponding infrastructure. We explore the problems of specifying, composing, reasoning about and implementing applications in such a system. A specific concern of our research is developing the infrastructure to support structuring distributed applications by using sequential, choice and parallel composition, in the anarchic environment where application compositions may be unforeseeable and interactions may be unknown prior to actually occurring. The structuring concepts discussed are relevant to a wide range of distributed applications; our implementation is illustrated with collaborative Java processes interacting over the Internet, but the methodology provided can be applied independent of specific platforms

hopCP: A concurrent hardware description language

Journal ArticlehopCP is a language for the specification, simulation, and synthesis of hardware systems. hopCP captures the behavior of a hardware system by specifying the causal relationships between actions that the system can perform. No specific timing discipline is implied by a hopCP specification. Hence, hopCP specifications can be implemented as synchronous, asynchronous, or mixed synchronous and asynchronous circuits. Salient features of hopCP include nonatomic actions, synchronous and asynchronous styles of value communication, broadcast channels, a purely functional sublanguage to express the computational aspects of hardware behavior, and an efficient tool (called parComp) to infer the composite behavior of a collection of hopCP modules. Operational Semantics of hopCP in terms of labeled transition systems is presented. A few examples are described to illustrate the expressive power of hopCP. A summary of the implementation is also presented

Engineering Parallel String Sorting

We discuss how string sorting algorithms can be parallelized on modern multi-core shared memory machines. As a synthesis of the best sequential string sorting algorithms and successful parallel sorting algorithms for atomic objects, we first propose string sample sort. The algorithm makes effective use of the memory hierarchy, uses additional word level parallelism, and largely avoids branch mispredictions. Then we focus on NUMA architectures, and develop parallel multiway LCP-merge and -mergesort to reduce the number of random memory accesses to remote nodes. Additionally, we parallelize variants of multikey quicksort and radix sort that are also useful in certain situations. Comprehensive experiments on five current multi-core platforms are then reported and discussed. The experiments show that our implementations scale very well on real-world inputs and modern machines.Comment: 46 pages, extension of "Parallel String Sample Sort" arXiv:1305.115

Debugging Process Algebra Specifications

International audienceDesigning and developing distributed and concurrent applications has always been a tedious and error-prone task. In this context, formal techniques and tools are of great help in order to specify such concurrent systems and detect bugs in the corresponding models. In this paper, we propose a new framework for debugging value-passing process algebra through coverage analysis. We illustrate our approach with LNT, which is a recent specification language designed for formally modelling concurrent systems. We define several coverage notions before showing how to instrument the specification without affecting original behaviors. Our approach helps one to improve the quality of a dataset of examples used for validation purposes, but also to find ill-formed decisions, dead code, and other errors in the specification. We have implemented a tool for automating our debugging approach, and applied it to several real-world case studies in different application areas

Collaborative Perception From Data Association To Localization

During the last decade, visual sensors have become ubiquitous. One or more cameras can be found in devices ranging from smartphones to unmanned aerial vehicles and autonomous cars. During the same time, we have witnessed the emergence of large scale networks ranging from sensor networks to robotic swarms. Assume multiple visual sensors perceive the same scene from different viewpoints. In order to achieve consistent perception, the problem of correspondences between ob- served features must be first solved. Then, it is often necessary to perform distributed localization, i.e. to estimate the pose of each agent with respect to a global reference frame. Having everything set in the same coordinate system and everything having the same meaning for all agents, operation of the agents and interpretation of the jointly observed scene become possible. The questions we address in this thesis are the following: first, can a group of visual sensors agree on what they see, in a decentralized fashion? This is the problem of collaborative data association. Then, based on what they see, can the visual sensors agree on where they are, in a decentralized fashion as well? This is the problem of cooperative localization. The contributions of this work are five-fold. We are the first to address the problem of consistent multiway matching in a decentralized setting. Secondly, we propose an efficient decentralized dynamical systems approach for computing any number of smallest eigenvalues and the associated eigenvectors of a weighted graph with global convergence guarantees with direct applications in group synchronization problems, e.g. permutations or rotations synchronization. Thirdly, we propose a state-of-the art framework for decentralized collaborative localization for mobile agents under the presence of unknown cross-correlations by solving a minimax optimization prob- lem to account for the missing information. Fourthly, we are the first to present an approach to the 3-D rotation localization of a camera sensor network from relative bearing measurements. Lastly, we focus on the case of a group of three visual sensors. We propose a novel Riemannian geometric representation of the trifocal tensor which relates projections of points and lines in three overlapping views. The aforemen- tioned representation enables the use of the state-of-the-art optimization methods on Riemannian manifolds and the use of robust averaging techniques for estimating the trifocal tensor