50,138 research outputs found
Fully Adaptive Gaussian Mixture Metropolis-Hastings Algorithm
Markov Chain Monte Carlo methods are widely used in signal processing and
communications for statistical inference and stochastic optimization. In this
work, we introduce an efficient adaptive Metropolis-Hastings algorithm to draw
samples from generic multi-modal and multi-dimensional target distributions.
The proposal density is a mixture of Gaussian densities with all parameters
(weights, mean vectors and covariance matrices) updated using all the
previously generated samples applying simple recursive rules. Numerical results
for the one and two-dimensional cases are provided
Backward chaining inference as a database stored procedure – the experiments on real-world knowledge bases
In this work, two approaches of backward chaining inference
implementation were compared. The first approach uses a
classical, goal-driven inference running on the client device – the
algorithm implemented within the KBExpertLib library was
used. Inference was performed on a rule base buffered in memory
structures. The second approach involves implementing inference
as a stored procedure, run in the environment of the database
server – an original, previously not published algorithm was
introduced. Experiments were conducted on real-world
knowledge bases with a relatively large number of rules.
Experiments were prepared so that one could evaluate the
pessimistic complexity of the inference algorithm. This work also
includes a detailed description of the classical backward inference
algorithm – the outline of the algorithm is presented as a block
diagram and in the form of pseudo-code. Moreover, a recursive
version of backward chaining is discussed
Type-Based Detection of XML Query-Update Independence
This paper presents a novel static analysis technique to detect XML
query-update independence, in the presence of a schema. Rather than types, our
system infers chains of types. Each chain represents a path that can be
traversed on a valid document during query/update evaluation. The resulting
independence analysis is precise, although it raises a challenging issue:
recursive schemas may lead to infer infinitely many chains. A sound and
complete approximation technique ensuring a finite analysis in any case is
presented, together with an efficient implementation performing the chain-based
analysis in polynomial space and time.Comment: VLDB201
A framework for deadlock detection in core ABS
We present a framework for statically detecting deadlocks in a concurrent
object-oriented language with asynchronous method calls and cooperative
scheduling of method activations. Since this language features recursion and
dynamic resource creation, deadlock detection is extremely complex and
state-of-the-art solutions either give imprecise answers or do not scale. In
order to augment precision and scalability we propose a modular framework that
allows several techniques to be combined. The basic component of the framework
is a front-end inference algorithm that extracts abstract behavioural
descriptions of methods, called contracts, which retain resource dependency
information. This component is integrated with a number of possible different
back-ends that analyse contracts and derive deadlock information. As a
proof-of-concept, we discuss two such back-ends: (i) an evaluator that computes
a fixpoint semantics and (ii) an evaluator using abstract model checking.Comment: Software and Systems Modeling, Springer Verlag, 201
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