46,516 research outputs found
Parallel machine architecture and compiler design facilities
The objective is to provide an integrated simulation environment for studying and evaluating various issues in designing parallel systems, including machine architectures, parallelizing compiler techniques, and parallel algorithms. The status of Delta project (which objective is to provide a facility to allow rapid prototyping of parallelized compilers that can target toward different machine architectures) is summarized. Included are the surveys of the program manipulation tools developed, the environmental software supporting Delta, and the compiler research projects in which Delta has played a role
Modelling of self-driven particles: foraging ants and pedestrians
Models for the behavior of ants and pedestrians are studied in an unified way
in this paper. Each ant follows pheromone put by preceding ants, hence creating
a trail on the ground, while pedestrians also try to follow others in a crowd
for efficient and safe walking. These following behaviors are incorporated in
our stochastic models by using only local update rules for computational
efficiency. It is demonstrated that the ant trail model shows an unusual
non-monotonic dependence of the average speed of the ants on their density,
which can be well analyzed by the zero-range process. We also show that this
anomalous behavior is clearly observed in an experiment of multiple robots.
Next, the relation between the ant trail model and the floor field model for
studying evacuation dynamics of pedestrians is discussed. The latter is
regarded as a two-dimensional generalization of the ant trail model, where the
pheromone is replaced by footprints.Comment: 15 pages, 11 Postscript figures, uses elsart.cl
Understanding object-oriented source code from the behavioural perspective
Comprehension is a key activity that underpins a variety of software maintenance and engineering tasks. The task of understanding object-oriented systems is hampered by the fact that the code segments that are related to a user-level function tend to be distributed across the system. We introduce a tool-supported code extraction technique that addresses this issue. Given a minimal amount of information about a behavioural element of the system that is of interest (such as a use-case), it extracts a trail of the methods (and method invocations) through the system that are needed in order to achieve an understanding of the implementation of the element of interest. We demonstrate the feasibility of our approach by implementing it as part of a code extraction tool, presenting a case study and evaluating the approach and tool against a set of established criteria for program comprehension tools
A Semantic Hierarchy for Erasure Policies
We consider the problem of logical data erasure, contrasting with physical
erasure in the same way that end-to-end information flow control contrasts with
access control. We present a semantic hierarchy for erasure policies, using a
possibilistic knowledge-based semantics to define policy satisfaction such that
there is an intuitively clear upper bound on what information an erasure policy
permits to be retained. Our hierarchy allows a rich class of erasure policies
to be expressed, taking account of the power of the attacker, how much
information may be retained, and under what conditions it may be retained.
While our main aim is to specify erasure policies, the semantic framework
allows quite general information-flow policies to be formulated for a variety
of semantic notions of secrecy.Comment: 18 pages, ICISS 201
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