Results 11  20
of
137
Optimum and Heuristic Transformation Techniques for Simultaneous Optimization of Latency and Throughput
 IEEE Trans. on VLSI Systems
, 1995
"... A common metric of speed for DSP systems is their throughput. Algorithm transformations are the key to obtaining high throughput ASIC as well as software implementations. However, increasingly DSP subsystems are being used in systems such as "signal processing servers" and embedded controllers where ..."
Abstract

Cited by 30 (3 self)
 Add to MetaCart
A common metric of speed for DSP systems is their throughput. Algorithm transformations are the key to obtaining high throughput ASIC as well as software implementations. However, increasingly DSP subsystems are being used in systems such as "signal processing servers" and embedded controllers where both throughput and latency are important, and independent, metrics of speed. For example, the subsystem implementing the control law in a robot controller is part of a feedback loop so that not only does it have to process the inputs arriving at a rate determined by the sample period of the control loop, but it also has to produce the output corresponding to an input sample within a specified latency constraint. Although throughput alone can be arbitrarily improved for several classes of systems using previously published techniques, none of those approaches are effective when latency constraints are considered. After formally establishing the relationship between latency and throughput in...
Geometry and Concurrency: A User's Guide
, 2000
"... Introduction "Geometry and Concurrency" is not yet a wellestablished domain of research, but is rather made of a collection of seemingly related techniques, algorithms and formalizations, coming from different application areas, accumulated over a long period of time. There is currently a certain ..."
Abstract

Cited by 28 (7 self)
 Add to MetaCart
Introduction "Geometry and Concurrency" is not yet a wellestablished domain of research, but is rather made of a collection of seemingly related techniques, algorithms and formalizations, coming from different application areas, accumulated over a long period of time. There is currently a certain amount of effort made for unifying these (in particular see the article (Gunawardena, 1994)), following the workshop "New Connections between Computer Science and Mathematics" held at the Newton Institute in Cambridge, England in November 1995 (and sponsored by HP/BRIMS). More recently, the first workshop on the very same subject has been held in Aalborg, Denmark (see http://www.math.auc.dk/~raussen/admin/workshop/workshop.html where the articles of this issue, among others, have been first sketched. But what is "Geometry and Concurrency" composed of then? It is an area of research made of techniques which use geometrical reasoning for describing and solving problems
Probabilistic event structures and domains
 Concurrency Theory: 15th International Conference, CONCUR ’04 Proceedings, LNCS
, 2004
"... This paper investigates probability in the presence of causal dependence. More precisely, it studies the process model of probabilistic event structures. In their simplest form probabilistic choice is localised to cells at which immediate conflict arises; in which case probabilistic independence coi ..."
Abstract

Cited by 27 (9 self)
 Add to MetaCart
This paper investigates probability in the presence of causal dependence. More precisely, it studies the process model of probabilistic event structures. In their simplest form probabilistic choice is localised to cells at which immediate conflict arises; in which case probabilistic independence coincides with causal independence. An event structure is associated with a domain—that of its configurations ordered by inclusion. In domain theory probabilistic processes are denoted by continuous valuations on a domain. A key result of this paper is a representation theorem showing how continuous valuations on the domain of a confusion free event structure correspond to the probabilistic event structures it supports. Via a notion of tests, probabilistic event structures are related to another approach to probabilistic processes, viz. Markov decision processes. Tests and morphisms of event structures point the way to a more general theory in which, for example, event structures need not be confusion free. 1
A Relational Model of NonDeterministic Dataflow
 In CONCUR'98, volume 1466 of LNCS
, 1998
"... . We recast dataflow in a modern categorical light using profunctors as a generalisation of relations. The well known causal anomalies associated with relational semantics of indeterminate dataflow are avoided, but still we preserve much of the intuitions of a relational model. The development fits ..."
Abstract

Cited by 27 (13 self)
 Add to MetaCart
. We recast dataflow in a modern categorical light using profunctors as a generalisation of relations. The well known causal anomalies associated with relational semantics of indeterminate dataflow are avoided, but still we preserve much of the intuitions of a relational model. The development fits with the view of categories of models for concurrency and the general treatment of bisimulation they provide. In particular it fits with the recent categorical formulation of feedback using traced monoidal categories. The payoffs are: (1) explicit relations to existing models and semantics, especially the usual axioms of monotone IO automata are read off from the definition of profunctors, (2) a new definition of bisimulation for dataflow, the proof of the congruence of which benefits from the preservation properties associated with open maps and (3) a treatment of higherorder dataflow as a biproduct, essentially by following the geometry of interaction programme. 1 Introduction A fundament...
A Denotational Semantics for Dataflow with Firing
 Memorandum UCB/ERL M97/ 3, Electronics Research
, 1997
"... Dataflow models of computation have intrigued computer scientists since the 1970s. They were first introduced by Jack Dennis as a basis for parallel programming languages and architectures, and by Gilles Kahn as a model of concurrency. Interest in these models of computation has been recently rekind ..."
Abstract

Cited by 26 (7 self)
 Add to MetaCart
Dataflow models of computation have intrigued computer scientists since the 1970s. They were first introduced by Jack Dennis as a basis for parallel programming languages and architectures, and by Gilles Kahn as a model of concurrency. Interest in these models of computation has been recently rekindled by the resurrection of parallel computing, due to the emergence of multicore architectures. However, Dennis and Kahn approached dataflow very differently. Dennis ’ approach was based on an operational notion of atomic firings driven by certain firing rules. Kahn’s approach was based on a denotational notion of processes as continuous functions on infinite streams. This paper bridges the gap between these two points of view, showing that sequences of firings define a continuous Kahn process as the least fixed point of an appropriately constructed functional. The Dennis firing rules are sets of finite prefixes satisfying certain conditions that ensure determinacy. These conditions result in firing rules that are strictly more general than the blocking reads of the KahnMacQueen implementation of Kahn process networks, and solve some compositionality problems in the dataflow model. 1
A Comparison of Synchronous and CycloStatic Dataflow
, 1995
"... We compare synchronous dataflow (SDF) and cyclostatic dataflow (CSDF), which are each special cases of a model of computation we call dataflow process networks. In SDF, actors have static firing rules: they consume and produce a fixed number of data tokens in each firing. This model is well suited ..."
Abstract

Cited by 25 (0 self)
 Add to MetaCart
We compare synchronous dataflow (SDF) and cyclostatic dataflow (CSDF), which are each special cases of a model of computation we call dataflow process networks. In SDF, actors have static firing rules: they consume and produce a fixed number of data tokens in each firing. This model is well suited to multirate signal processing applications and lends itself to efficient, static scheduling, avoiding the runtime scheduling overhead incurred by general implementations of process networks. In CSDF, which is a generalization of SDF, actors have cyclicly changing firing rules. In some situations, the added generality of CSDF can unnecessarily complicate scheduling. We show how higherorder functions can be used to transform a CSDF graph into a SDF graph, simplifying the scheduling problem. In other situations, CSDF has a genuine advantage over SDF: simpler precedence constraints. We show how this makes it possible to eliminate unnecessary computations and expose additional parallelism. We use digital sample rate conversion as an example to illustrate these advantages of CSDF.
Turing Machines, Transition Systems, and Interaction
 Information and Computation
, 2004
"... We present Persistent Turing Machines (PTMs), a new way of interpreting Turingmachine computation, one that is both interactive and persistent. A PTM repeatedly receives an input token from the environment, computes for a while, and then outputs the result. Moreover, it can \remember" its previo ..."
Abstract

Cited by 25 (3 self)
 Add to MetaCart
We present Persistent Turing Machines (PTMs), a new way of interpreting Turingmachine computation, one that is both interactive and persistent. A PTM repeatedly receives an input token from the environment, computes for a while, and then outputs the result. Moreover, it can \remember" its previous state (worktape contents) upon commencing a new computation. We show that the class of PTMs is isomorphic to a very general class of eective transition systems, thereby allowing one to view PTMs as transition systems \in disguise." The persistent stream language (PSL) of a PTM is a coinductively dened set of interaction streams : innite sequences of pairs of the form (w i ; w o ), recording, for each interaction with the environment, the input token received by the PTM and the corresponding output token. We dene an innite hierarchy of successively ner equivalences for PTMs over nite interactionstream prexes and show that the limit of this hierarchy does not coincide with PSLequivalence. The presence of this \gap" can be attributed to the fact that the transition systems corresponding to PTM computations naturally exhibit unbounded nondeterminism. We also consider amnesic PTMs, where each new computation begins with a blank work tape, and a corresponding notion of equivalence based on amnesic stream languages (ASLs). We show that the class of ASLs is strictly contained in the class of PSLs. Amnesic stream languages are representative of the classical view of Turingmachine computation. One may consequently conclude that, in a streambased setting, the extension of the Turingmachine model with persistence is a nontrivial one, and provides a formal foundation for reasoning about programming concepts such as objects with static elds. We additional...
Compositional Parallel Programming Languages
 ACM TRANSACTIONS ON PROGRAMMING LANGUAGES AND SYSTEMS
, 1999
"... ... this paper, we discuss alternative approaches to the realization of this principle, which holds that properties of program components should be preserved when those components are composed in parallel with other program components. We review two programming languages, Strand and Program Composit ..."
Abstract

Cited by 23 (3 self)
 Add to MetaCart
... this paper, we discuss alternative approaches to the realization of this principle, which holds that properties of program components should be preserved when those components are composed in parallel with other program components. We review two programming languages, Strand and Program Composition Notation, that support compositionality via a small number of simple concepts, namely monotone operations on shared objects, a uniform addressing mechanism, and parallel composition. Both languages have been used extensively for largescale application development, allowing us to provide an informed assessment of their strengths and weaknesses. We observe that while compositionality simplifies development of complex applications, the use of specialized languages hinders reuse of existing code and tools, and the specification of domain decomposition strategies. This suggests an alternative approach based on small extensions to existing sequential languages. We conclude the paper with a discussion of two languages that realize this strategy.
Models of Computation and Languages for Embedded System Design
, 2005
"... We review Models of Computation (MoC) and organize them with respect to the time abstraction they use. We distinguish between continuous time, discrete time, synchronous and untimed MoCs. System level models serve a variety of objectives with partially contradicting requirements. Consequently we arg ..."
Abstract

Cited by 22 (1 self)
 Add to MetaCart
We review Models of Computation (MoC) and organize them with respect to the time abstraction they use. We distinguish between continuous time, discrete time, synchronous and untimed MoCs. System level models serve a variety of objectives with partially contradicting requirements. Consequently we argue that different MoCs are necessary for the various tasks and phases in the design of an embedded system. Moreover, different MoCs have to be integrated to provide a coherent system modeling and analysis environment. We discuss the relation between some popular languages and the reviewed MoCs to find that a given MoC is offered by many languages and a single language can support multiple MoCs. We contend that it is of importance for the quality of tools and overall design productivity, which abstraction levels and which primitive operators are provided in a language. However, we also observe that there are various flexible ways to do this, e.g. by way of heterogeneous frameworks, coordination languages and embedding of different MoCs in the same language.
A model for useroriented data provenance in pipelined scientific workflows
 IN IPAW
, 2006
"... Integrated provenance support promises to be a chief advantage of scientific workflow systems over scriptbased alternatives. While it is often recognized that information gathered during scientific workflow execution can be used automatically to increase fault tolerance (via checkpointing) and to o ..."
Abstract

Cited by 22 (8 self)
 Add to MetaCart
Integrated provenance support promises to be a chief advantage of scientific workflow systems over scriptbased alternatives. While it is often recognized that information gathered during scientific workflow execution can be used automatically to increase fault tolerance (via checkpointing) and to optimize performance (by reusing intermediate data products in future runs), it is perhaps more significant that provenance information also may be used by scientists to reproduce results from earlier runs, to explain unexpected results, and to prepare results for publication. Current workflow systems offer little or no direct support for these “scientistoriented ” queries of provenance information. Indeed the use of advanced execution models in scientific workflows (e.g., process networks, which exhibit pipeline parallelism over streaming data) and failure to record certain fundamental events such as state resets of processes, can render existing provenance schemas useless for scientific applications of provenance. We develop a simple provenance model that is capable of supporting a wide range of scientific use cases even for complex models of computation such as process networks. Our approach reduces these use cases to database queries over event logs, and is capable of reconstructing complete data and invocation dependency graphs for a workflow run.