180,915 research outputs found
Using Session Types for Reasoning About Boundedness in the Pi-Calculus
The classes of depth-bounded and name-bounded processes are fragments of the
pi-calculus for which some of the decision problems that are undecidable for
the full calculus become decidable. P is depth-bounded at level k if every
reduction sequence for P contains successor processes with at most k active
nested restrictions. P is name-bounded at level k if every reduction sequence
for P contains successor processes with at most k active bound names.
Membership of these classes of processes is undecidable. In this paper we use
binary session types to decise two type systems that give a sound
characterization of the properties: If a process is well-typed in our first
system, it is depth-bounded. If a process is well-typed in our second, more
restrictive type system, it will also be name-bounded.Comment: In Proceedings EXPRESS/SOS 2017, arXiv:1709.0004
Compositional Reasoning for Explicit Resource Management in Channel-Based Concurrency
We define a pi-calculus variant with a costed semantics where channels are
treated as resources that must explicitly be allocated before they are used and
can be deallocated when no longer required. We use a substructural type system
tracking permission transfer to construct coinductive proof techniques for
comparing behaviour and resource usage efficiency of concurrent processes. We
establish full abstraction results between our coinductive definitions and a
contextual behavioural preorder describing a notion of process efficiency
w.r.t. its management of resources. We also justify these definitions and
respective proof techniques through numerous examples and a case study
comparing two concurrent implementations of an extensible buffer.Comment: 51 pages, 7 figure
Work-in-progress Assume-guarantee reasoning with ioco
This paper presents a combination between the assume-guarantee paradigm and the testing relation ioco. The assume-guarantee paradigm is a ”divide and conquer” technique that decomposes the verification of a system into smaller tasks that involve the verification of its components. The principal aspect of assume-guarantee reasoning is to consider each component separately, while taking into account assumptions about the context of the component. The testing relation ioco is a formal conformance relation for model-based testing that works on labeled transition systems. Our main result shows that, with certain restrictions, assume-guarantee reasoning can be applied in the context of ioco. This enables testing ioco-conformance of a system by testing its components separately
Characteristic Bisimulation for Higher-Order Session Processes
Characterising contextual equivalence is a long-standing issue for higher-order (process) languages. In the setting of a higher-order pi-calculus with sessions, we develop characteristic bisimilarity, a typed bisimilarity which fully characterises contextual equivalence. To our knowledge, ours is the first characterisation of its kind. Using simple values inhabiting (session) types, our approach distinguishes from untyped methods for characterising contextual equivalence in higher-order processes: we show that observing as inputs only a precise finite set of higher-order values suffices to reason about higher-order session processes. We demonstrate how characteristic bisimilarity can be used to justify optimisations in session protocols with mobile code communication
Deep Reinforcement Learning on a Budget: 3D Control and Reasoning Without a Supercomputer
An important goal of research in Deep Reinforcement Learning in mobile
robotics is to train agents capable of solving complex tasks, which require a
high level of scene understanding and reasoning from an egocentric perspective.
When trained from simulations, optimal environments should satisfy a currently
unobtainable combination of high-fidelity photographic observations, massive
amounts of different environment configurations and fast simulation speeds. In
this paper we argue that research on training agents capable of complex
reasoning can be simplified by decoupling from the requirement of high fidelity
photographic observations. We present a suite of tasks requiring complex
reasoning and exploration in continuous, partially observable 3D environments.
The objective is to provide challenging scenarios and a robust baseline agent
architecture that can be trained on mid-range consumer hardware in under 24h.
Our scenarios combine two key advantages: (i) they are based on a simple but
highly efficient 3D environment (ViZDoom) which allows high speed simulation
(12000fps); (ii) the scenarios provide the user with a range of difficulty
settings, in order to identify the limitations of current state of the art
algorithms and network architectures. We aim to increase accessibility to the
field of Deep-RL by providing baselines for challenging scenarios where new
ideas can be iterated on quickly. We argue that the community should be able to
address challenging problems in reasoning of mobile agents without the need for
a large compute infrastructure
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