101,241 research outputs found
Computer architectures for functional and logic languages
PhD ThesisIn recent years interest in functional and logic languages has
grown considerably. Both classes of language offer advantages for programming
and have an influential group of people promoting them. As yet
no consensus has formed as to which class is best, and such a consensus
may never form. Future general-purpose computer architectures may well
be required to support both classes of language efficiently. Novel
architectures designed to support both classes of languages could even
add impetus to the area of hybrid functional/logic languages.
Treleaven et al[68] have proposed a classification of computational
mechanisms which they believe underly several types of novel computer
architecture (i.e. control flow, data flow and reduction). The classification
partitions novel general-purpose architectures into the following
classes: control driven - where a statement is executed when it is
selected by flow(s) of control, data driven - where a statement is executed
when some combination of its arguments are available, and demand
driven - where a statement is executed when the result it produces is
needed by another, already active instruction.
This thesis investigates the efficient support of both functional
and logic languages using an architecture that attempts to be general
purpose by embodying all the mechanisms that underly the above classification.
A novel packet communication architecture is presented which intergrates
the control driven, data driven and demand driven computational
mechanisms. A software emulator for the machine was used as the basis
for separate implementations of functional and logic languages, which
were in turn used to evaluate the effectiveness of the computational
mechanisms described in the classification. These mechanisms allowed
functional languages to be implemented wi th ease, but caused severe
problems when used to support logic languages. The difficulties with
these mechanisms are taken as signifying that they do not provide adequate
support for logic languages. The problems encountered led to the
development of a novel implementation technique for logic languages,
which also proved to be a good basis for a combined functional and logic
model. This model is believed to provide a sound foundation for a
parallel computer system that would support functional and logic
languages with equal elegance and efficiency, and would therefore also
support hybrid languages. The design for such a computer is described
at the end of this thesis.the Science and Engineering Research Council, Great Britain
A parallel process model and architecture for a Pure Logic Language
The research presented in this thesis has been concerned with the use of parallel logic systems for the implementation of large knowledge bases. The thesis describes proposals for a parallel logic system based on a new logic programming language, the Pure Logic Language. The work has involved the definition and implementation of a new logic interpreter which incorporates the parallel execution of independent OR processes, and the specification and design of an appropriate non shared memory multiprocessor architecture.
The Pure Logic Language which is under development at JeL, Bracknell, differs from Prolog in its expressive powers and implementation. The resolution based Prolog approach is replaced by a rewrite rule technique which successively transforms expressions according to logical axioms and user defined rules until no further rewrites are possible.
A review of related work in the field of parallel logic language systems is presented. The thesis describes the different forms of parallelism within logic languages and discusses the decision to concentrate on the efficient implementation of OR parallelism. The parallel process model for the Pure Logic Language uses the same execution technique of rule rewriting but has been adapted to implement the creation of independent OR processes and the required message passing operations. The parallelism in the system is implemented automatically and, unlike many other parallel logic systems there are no explicit program annotations for the control of parallel execution. The spawning of processes involves computational overheads within the interpreter: these have been measured and results are presented.
The functional requirements of a multiprocessor architecture are discussed: shared memory machines are not scalable for large numbers of processing elements, but, with no shared memory, data needed by offspring processors must be copied from the parent or else recomputed. The thesis describes an optimised format for the copying of data between processors. Because a one-to-many communication pattern exits between parent and offspring processors a broadcast architecture is indicated. The development of a system based on the broadcasting of data packets represents a new approach to the parallel execution of logic languages and has led to the design of a novel bus based multiprocessor architecture. A simulation of this multiprocessor architecture has been produced and the parallel logic interpreter mapped onto it: this provides data on the predicted performance of the system. A detailed analysis of these results is presented and the implications for future developments to the proposed system are discussed.</p
Abstract State Machines 1988-1998: Commented ASM Bibliography
An annotated bibliography of papers which deal with or use Abstract State
Machines (ASMs), as of January 1998.Comment: Also maintained as a BibTeX file at http://www.eecs.umich.edu/gasm
CREOLE: a Universal Language for Creating, Requesting, Updating and Deleting Resources
In the context of Service-Oriented Computing, applications can be developed
following the REST (Representation State Transfer) architectural style. This
style corresponds to a resource-oriented model, where resources are manipulated
via CRUD (Create, Request, Update, Delete) interfaces. The diversity of CRUD
languages due to the absence of a standard leads to composition problems
related to adaptation, integration and coordination of services. To overcome
these problems, we propose a pivot architecture built around a universal
language to manipulate resources, called CREOLE, a CRUD Language for Resource
Edition. In this architecture, scripts written in existing CRUD languages, like
SQL, are compiled into Creole and then executed over different CRUD interfaces.
After stating the requirements for a universal language for manipulating
resources, we formally describe the language and informally motivate its
definition with respect to the requirements. We then concretely show how the
architecture solves adaptation, integration and coordination problems in the
case of photo management in Flickr and Picasa, two well-known service-oriented
applications. Finally, we propose a roadmap for future work.Comment: In Proceedings FOCLASA 2010, arXiv:1007.499
A Simulation Tool for tccp Programs
The Timed Concurrent Constraint Language tccp is a declarative synchronous concurrent language, particularly suitable for modelling reactive systems. In tccp, agents communicate and synchronise through a global constraint store. It supports a notion of discrete time that allows all non-blocked agents to proceed with their execution simultaneously.
In this paper, we present a modular architecture for the simulation of tccp programs. The tool comprises three main components. First, a set of basic abstract instructions able to model the tccp agent behaviour, the memory model needed to manage the active agents and the state of the store during the execution. Second, the agent interpreter that executes the instructions of the current agent iteratively and calculates the new agents to be executed at the next time instant. Finally, the constraint solver components which are the modules that deal with constraints.
In this paper, we describe the implementation of these components and present an example of a real system modelled in tccp.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
Parallel VLSI architecture emulation and the organization of APSA/MPP
The Applicative Programming System Architecture (APSA) combines an applicative language interpreter with a novel parallel computer architecture that is well suited for Very Large Scale Integration (VLSI) implementation. The Massively Parallel Processor (MPP) can simulate VLSI circuits by allocating one processing element in its square array to an area on a square VLSI chip. As long as there are not too many long data paths, the MPP can simulate a VLSI clock cycle very rapidly. The APSA circuit contains a binary tree with a few long paths and many short ones. A skewed H-tree layout allows every processing element to simulate a leaf cell and up to four tree nodes, with no loss in parallelism. Emulation of a key APSA algorithm on the MPP resulted in performance 16,000 times faster than a Vax. This speed will make it possible for the APSA language interpreter to run fast enough to support research in parallel list processing algorithms
Applying Formal Methods to Networking: Theory, Techniques and Applications
Despite its great importance, modern network infrastructure is remarkable for
the lack of rigor in its engineering. The Internet which began as a research
experiment was never designed to handle the users and applications it hosts
today. The lack of formalization of the Internet architecture meant limited
abstractions and modularity, especially for the control and management planes,
thus requiring for every new need a new protocol built from scratch. This led
to an unwieldy ossified Internet architecture resistant to any attempts at
formal verification, and an Internet culture where expediency and pragmatism
are favored over formal correctness. Fortunately, recent work in the space of
clean slate Internet design---especially, the software defined networking (SDN)
paradigm---offers the Internet community another chance to develop the right
kind of architecture and abstractions. This has also led to a great resurgence
in interest of applying formal methods to specification, verification, and
synthesis of networking protocols and applications. In this paper, we present a
self-contained tutorial of the formidable amount of work that has been done in
formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial
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