129 research outputs found
Compiling CSP
No full textCSP, Hoare's Communicating Sequential Processes, is a formal language for specifying, implementing and reasoning about concurrent processes and their interactions. Existing software tools that deal with CSP directly are largely concerned with assisting formal proofs. This paper presents an alternative use for CSP, namely the compilation of CSP systems to executable code. The main motivation for this work is in providing a means to experiment with relatively large CSP systems, possibly consisting millions of concurrent processes --- something that is hard to achieve with the tools currently available
Guppy: Process-Oriented Programming on Embedded Devices
No full textGuppy is a new and experimental process-oriented programming language, taking much inspiration (and some code-base) from the existing occam-pi language. This paper reports on a variety of aspects related to this, specifically language, compiler and run-time system development, enabling Guppy programs to run on desktop and embedded systems. A native code-generation approach is taken, using C as the intermediate language, and with stack-space requirements determined at compile-time
Video Processing in occam-pi
No full textThe occam-pi language provides many novel features for concurrent software development. This paper describes a video processing framework that explores the use of these features for multimedia applications. Processes are used to encapsulate operations on video and audio streams; mobile data types are used to transfer data between them efficiently, and mobile channels allow the process network to be dynamically reconfigured at runtime. We present demonstration applications including an interactive video player. Preliminary benchmarks show that the framework has comparable overhead to multimedia systems programmed using traditional methods
A CSP Model for Mobile Channels
No full textCSP processes have a static view of their environment -- a fixed set of events through which they synchronise with each other. In contrast, the pi-calculus is based on the dynamic construction of events (channels) and their distribution over pre-existing channels. In this way, process networks can be constructed dynamically with processes acquiring new connectivity. For the construction of complex systems, such as Internet trading and the modeling of living organisms, such capabilities have an obvious attraction. The occam-pi multiprocessing language is built upon classical occam, whose design and semantics are founded on CSP. To address the dynamics of complex systems, occam-pi extensions enable the movement of channels (and multiway synchronisation barriers) through channels, with constraints in line with previous occam discipline for safe and efficient programming. This paper reconciles these extensions by building a formal (operational) semantics for mobile channels entirely within CSP. These semantics provide two benefits: formal analysis of occam-pi systems using mobile channels and formal specification of implementation mechanisms for mobiles used by the occam-pi compiler and run-time kernel
Exploring GPGPU Acceleration of Process-Oriented Simulations
No full textThis paper reports on our experiences of using commodity GPUs to speed-up the execution of fine-grained concurrent simulations. Starting with an existing process-oriented `boids' simulation, we explore a variety of techniques aimed at improving performance, gradually refactoring the original code. Successive improvements lead to a 10-fold improvement in performance, which we believe can still be improved upon, allowing us to explore simulations with larger numbers of agents (30,000 rather than 2,000) interactively and without significant performance degradation
Mobile Escape Analysis for occam-pi
No full textEscape analysis is the process of discovering boundaries of dynamically allocated objects in programming languages. For object-oriented languages such as C++ and Java, this analysis leads to an understanding of which program objects interact directly, as well as what objects hold references to other objects. Such information can be used to help verify the correctness of an implementation with respect to its design, or provide information to a run-time system about which objects can be allocated on the stack (because they do not `escape' the method in which they are declared). For existing object-oriented languages, this analysis is typically made difficult by aliasing endemic to the language, and is further complicated by inheritance and polymorphism. In contrast, the occam-pi programming language is a process-oriented language, with systems built from layered networks of communicating concurrent processes. The language has a strong relationship with the CSP process algebra, that can be used to reason formally about the correctness of occam-pi programs. This paper presents early work on a compositional escape analysis technique for mobiles in the occam-pi programming language, in a style not dissimilar to existing CSP analyses. The primary aim is to discover the boundaries of mobiles within the communication graph, and to determine whether or not they escape any particular process or network of processes. The technique is demonstrated by analysing some typical occam-pi processes and networks, giving a formal understanding of their mobile escape behaviour
An Evaluation of Intel's Restricted Transactional Memory for CPAs
No full textWith the release of their latest processor microarchitecture, codenamed Haswell, Intel added new Transactional Synchronization Extensions (TSX) to their processors' instruction set. These extensions include support for Restricted Transactional Memory (RTM), a programming model in which arbitrary sized units of memory can be read and written in an atomic manner. This paper describes the low-level RTM programming model, benchmarks the performance of its instructions and speculates on how it may be used to implement and enhance Communicating Process Architectures
pony - The occam-pi Network Environment
No full textAlthough concurrency is generally perceived to be a `hard' subject, it can in fact be very simple --- provided that the underlying model is simple. The occam-pi parallel processing language provides such a simple yet powerful concurrency model that is based on CSP and the pi-calculus. This paper presents pony, the occam-pi Network Environment. occam-pi and pony provide a new, unified, concurrency model that bridges inter- and intra-processor concurrency. This enables the development of distributed applications in a transparent, dynamic and highly scalable way. The first part of this paper discusses the philosophy behind pony, explains how it is used, and gives a brief overview of its implementation. The second part evaluates pony's performance by presenting a number of benchmarks
Mobile Data, Dynamic Allocation and Zero Aliasing: an occam Experiment
No full textF.R.M. Barnes and P.H. Welch Communicating Process Architectures 2001 (WoTUG 24) Traditional imperative languages (such as C) and modern object-oriented languages are plagued by uncontrolled resource aliasing problems. Add in concurrency and the problems compound exponentially. Improperly synchronised access to shared (i.e. aliased) resources leads to problems of race-hazard, deadlock, livelock and starvation. This paper describes the binding into occam (a concurrent processing language based on CSP) of a secure, dynamic and efficient way of sharing data between parallel processes with minimal synchronisation overheads. The key new facilities provided are: a movement semantics for assignment and communication, strict zero-aliasing, apparently dynamic memory allocation and automatic zero-or-very-small-unit-time garbage collection. The implementation of this mechanism is also presented, along with some initial performance figures (e.g. 80ns for mobile communication on an 800 MHz Pentium 3). With occam becoming available on a variety of microprocessors for GUI building, internet services and small-memory-footprint embedded products, these capabilities are timely. Lessons are drawn for concurrency back in OO languages - and especially for the JCSP (CSP for Java) package library
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