716 research outputs found
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Compositional Dataflow Circuits
We present a technique for implementing dataflow networks as compositional hardware circuits. We first define an abstract dataflow model with unbounded buffers that supports data-dependent blocks (mux, demux, and nondeterministic merge); we then show how to faithfully implement such networks with bounded buffers and handshaking. Handshaking admits compositionality: our circuits can be connected with or without buffers, and combinational cycles arise only from a completely unbuffered cycle. While bounding buffer sizes can cause the system to deadlock prematurely, the system is guaranteed to produce the same, correct, data before then. Thus, unless the system deadlocks, inserting or removing buffers only affects its performance. We demonstrate how this enables design space to be explored
Handshaking Protocol for Distributed Implementation of Reo
Reo, an exogenous channel-based coordination language, is a model for service
coordination wherein services communicate through connectors formed by joining
binary communication channels. In order to establish transactional
communication among services as prescribed by connector semantics, distributed
ports exchange handshaking messages signalling which parties are ready to
provide or consume data. In this paper, we present a formal implementation
model for distributed Reo with communication delays and outline ideas for its
proof of correctness. To reason about Reo implementation formally, we introduce
Timed Action Constraint Automata (TACA) and explain how to compare TACA with
existing automata-based semantics for Reo. We use TACA to describe handshaking
behavior of Reo modeling primitives and argue that in any distributed circuit
remote Reo nodes and channels exposing such behavior commit to perform
transitions envisaged by the network semantics.Comment: In Proceedings FOCLASA 2014, arXiv:1502.0315
A compositional theory of digital circuits
A theory is compositional if complex components can be constructed out of
simpler ones on the basis of their interfaces, without inspecting their
internals. Digital circuits, despite being studied for nearly a century and
used at scale for about half that time, have until recently evaded a fully
compositional theoretical understanding. The sticking point has been the need
to avoid feedback loops that bypass memory elements, the so called
'combinational feedback' problem. This requires examining the internal
structure of a circuit, defeating compositionality. Recent work remedied this
theoretical shortcoming by showing how digital circuits can be presented
compositionally as morphisms in a freely generated Cartesian traced (or
dataflow) category. The focus was to support a better syntactical understanding
of digital circuits, culminating in the formulation of novel operational
semantics for digital circuits. In this paper we shift the focus onto the
denotational theory of such circuits, interpreting them as functions on streams
with to certain properties. These ensure that the model is fully abstract, i.e.
the equational theory and the semantic model are in perfect agreement. To
support this result we introduce two key equations: the first can reduce
circuits with combinational feedback to circuits without combinational feedback
via finite unfoldings of the loop, and the second can translate between open
circuits with the same behaviour syntactically by reducing the problem to
checking a finite number of closed circuits. The most important consequence of
this new semantics is that we can now give a recipe that ensures a circuit
always produces observable output, thus using the denotational model to inform
and improve the operational semantics.Comment: Restructured and refined presentation, 21 page
Reo + mCRL2: A Framework for Model-Checking Dataflow in Service Compositions
The paradigm of service-oriented computing revolutionized the field of software
engineering. According to this paradigm, new systems are composed of existing
stand-alone services to support complex cross-organizational business
processes. Correct communication of these services is not possible without a
proper coordination mechanism. The Reo coordination language is a channel-based
modeling language that introduces various types of channels and their
composition rules. By composing Reo channels, one can specify Reo connectors
that realize arbitrary complex behavioral protocols. Several formalisms have
been introduced to give semantics to Reo. In their most basic form, they
reflect service synchronization and dataflow constraints imposed by connectors.
To ensure that the composed system behaves as intended, we need a wide range of
automated verification tools to assist service composition designers. In this
paper, we present our framework for the verification of Reo using the mCRL2
toolset. We unify our previous work on mapping various semantic models for Reo,
namely, constraint automata, timed constraint automata, coloring semantics and
the newly developed action constraint automata, to the process algebraic
specification language of mCRL2, address the correctness of this mapping,
discuss tool support, and present a detailed example that illustrates the use
of Reo empowered with mCRL2 for the analysis of dataflow in service-based
process models
Reo + mCRL2: A Framework for Model-checking Dataflow in Service Compositions
The paradigm of service-oriented computing revolutionized the field of software engineering. According to this paradigm, new systems are composed of existing stand-alone services to support complex cross-organizational business processes. Correct communication of these services is not possible without a proper coordination mechanism. The Reo coordination language is a channel-based modeling language that introduces various types of channels and their composition rules. By composing Reo channels, one can specify Reo connectors that realize arbitrary complex behavioral protocols. Several formalisms have been introduced to give semantics to Reo. In their most basic form, they reflect service synchronization and dataflow constraints imposed by connectors. To ensure that the composed system behaves as intended, we need a wide range of automated verification tools to assist service composition designers. In this paper, we present our framework for the verification of Reo using the toolset. We unify our previous work on mapping various semantic models for Reo, namely, constraint automata, timed constraint automata, coloring semantics and the newly developed action constraint automata, to the process algebraic specification language of , address the correctness of this mapping, discuss tool support, and present a detailed example that illustrates the use of Reo empowered with for the analysis of dataflow in service-based process models
Tierkreis: A Dataflow Framework for Hybrid Quantum-Classical Computing
We present Tierkreis, a higher-order dataflow graph program representation
and runtime designed for compositional, quantum-classical hybrid algorithms.
The design of the system is motivated by the remote nature of quantum
computers, the need for hybrid algorithms to involve cloud and distributed
computing, and the long-running nature of these algorithms. The graph-based
representation reflects how designers reason about and visualise algorithms,
and allows automatic parallelism and asynchronicity. A strong, static type
system and higher-order semantics allow for high expressivity and
compositionality in the program. The flexible runtime protocol enables
third-party developers to add functionality using any language or environment.
With Tierkreis, quantum software developers can easily build, visualise,
verify, test, and debug complex hybrid workflows, and immediately deploy them
to the cloud or a custom distributed environment.Comment: Submitted to SC22 Workshop: Quantum Computing Softwar
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Deterministic Receptive Processes are Kahn Processes
Deterministic asynchronous concurrent formalisms are valuable because determinism greatly simplifies the design and validation of such systems and most concurrent formalisms are nondeterministic. This paper connects two of the more successful deterministic asynchronous formalisms: Kahn's dataflow networks and Josephs's deterministic receptive processes. The main result: a divergence-free deterministic receptive process is a Kahn process in that it can be modeled by a continuous function from input to output sequences, thus verifying it is compositionally deterministic. This result provides a bridge between two communities, enabling results from the asynchronous digital hardware community to be used in the context of dataflow computation and vice versa
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