3,567 research outputs found
Decidability of All Minimal Models (Revised Version - 2012)
This unpublished note is an alternate, shorter (and hopefully more readable)
proof of the decidability of all minimal models. The decidability follows from
a proof of the existence of a cellular term in each observational equivalence
class of a minimal model
Decidability of higher-order matching
We show that the higher-order matching problem is decidable using a
game-theoretic argument.Comment: appears in LMCS (Logical Methods in Computer Science
Reachability under Contextual Locking
The pairwise reachability problem for a multi-threaded program asks, given
control locations in two threads, whether they can be simultaneously reached in
an execution of the program. The problem is important for static analysis and
is used to detect statements that are concurrently enabled. This problem is in
general undecidable even when data is abstracted and when the threads (with
recursion) synchronize only using a finite set of locks. Popular programming
paradigms that limit the lock usage patterns have been identified under which
the pairwise reachability problem becomes decidable. In this paper, we consider
a new natural programming paradigm, called contextual locking, which ties the
lock usage to calling patterns in each thread: we assume that locks are
released in the same context that they were acquired and that every lock
acquired by a thread in a procedure call is released before the procedure
returns. Our main result is that the pairwise reachability problem is
polynomial-time decidable for this new programming paradigm as well. The
problem becomes undecidable if the locks are reentrant; reentrant locking is a
\emph{recursive locking} mechanism which allows a thread in a multi-threaded
program to acquire the reentrant lock multiple times.Comment: A preliminary version appears in TACAS 201
Gradual Certified Programming in Coq
Expressive static typing disciplines are a powerful way to achieve
high-quality software. However, the adoption cost of such techniques should not
be under-estimated. Just like gradual typing allows for a smooth transition
from dynamically-typed to statically-typed programs, it seems desirable to
support a gradual path to certified programming. We explore gradual certified
programming in Coq, providing the possibility to postpone the proofs of
selected properties, and to check "at runtime" whether the properties actually
hold. Casts can be integrated with the implicit coercion mechanism of Coq to
support implicit cast insertion a la gradual typing. Additionally, when
extracting Coq functions to mainstream languages, our encoding of casts
supports lifting assumed properties into runtime checks. Much to our surprise,
it is not necessary to extend Coq in any way to support gradual certified
programming. A simple mix of type classes and axioms makes it possible to bring
gradual certified programming to Coq in a straightforward manner.Comment: DLS'15 final version, Proceedings of the ACM Dynamic Languages
Symposium (DLS 2015
The effect of time on ear biometrics
We present an experimental study to demonstrate the effect of the time difference in image acquisition for gallery and probe on the performance of ear recognition. This experimental research is the first study on the time effect on ear biometrics. For the purpose of recognition, we convolve banana wavelets with an ear image and then apply local binary pattern on the convolved image. The histograms of the produced image are then used as features to describe an ear. A histogram intersection technique is then applied on the histograms of two ears to measure the ear similarity for the recognition purposes. We also use analysis of variance (ANOVA) to select features to identify the best banana wavelets for the recognition process. The experimental results show that the recognition rate is only slightly reduced by time. The average recognition rate of 98.5% is achieved for an eleven month-difference between gallery and probe on an un-occluded ear dataset of 1491 images of ears selected from Southampton University ear database
Reachability Analysis of Communicating Pushdown Systems
The reachability analysis of recursive programs that communicate
asynchronously over reliable FIFO channels calls for restrictions to ensure
decidability. Our first result characterizes communication topologies with a
decidable reachability problem restricted to eager runs (i.e., runs where
messages are either received immediately after being sent, or never received).
The problem is EXPTIME-complete in the decidable case. The second result is a
doubly exponential time algorithm for bounded context analysis in this setting,
together with a matching lower bound. Both results extend and improve previous
work from La Torre et al
Rewriting Modulo \beta in the \lambda\Pi-Calculus Modulo
The lambda-Pi-calculus Modulo is a variant of the lambda-calculus with
dependent types where beta-conversion is extended with user-defined rewrite
rules. It is an expressive logical framework and has been used to encode logics
and type systems in a shallow way. Basic properties such as subject reduction
or uniqueness of types do not hold in general in the lambda-Pi-calculus Modulo.
However, they hold if the rewrite system generated by the rewrite rules
together with beta-reduction is confluent. But this is too restrictive. To
handle the case where non confluence comes from the interference between the
beta-reduction and rewrite rules with lambda-abstraction on their left-hand
side, we introduce a notion of rewriting modulo beta for the lambda-Pi-calculus
Modulo. We prove that confluence of rewriting modulo beta is enough to ensure
subject reduction and uniqueness of types. We achieve our goal by encoding the
lambda-Pi-calculus Modulo into Higher-Order Rewrite System (HRS). As a
consequence, we also make the confluence results for HRSs available for the
lambda-Pi-calculus Modulo.Comment: In Proceedings LFMTP 2015, arXiv:1507.0759
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