23,834 research outputs found
Finding a boundary between valid and invalid regions of the input space
In the context of robustness testing, the boundary between the valid and
invalid regions of the input space can be an interesting source of erroneous
inputs. Knowing where a specific software under test (SUT) has a boundary is
essential for validation in relation to requirements. However, finding where a
SUT actually implements the boundary is a non-trivial problem that has not
gotten much attention. This paper proposes a method of finding the boundary
between the valid and invalid regions of the input space. The proposed method
consists of two steps. First, test data generators, directed by a search
algorithm to maximise distance to known, valid test cases, generate valid test
cases that are closer to the boundary. Second, these valid test cases undergo
mutations to try to push them over the boundary and into the invalid part of
the input space. This results in a pair of test sets, one consisting of test
cases on the valid side of the boundary and a matched set on the outer side,
with only a small distance between the two sets. The method is evaluated on a
number of examples from the standard library of a modern programming language.
We propose a method of determining the boundary between valid and invalid
regions of the input space and apply it on a SUT that has a non-contiguous
valid region of the input space. From the small distance between the developed
pairs of test sets, and the fact that one test set contains valid test cases
and the other invalid test cases, we conclude that the pair of test sets
described the boundary between the valid and invalid regions of that input
space. Differences of behaviour can be observed between different distances and
sets of mutation operators, but all show that the method is able to identify
the boundary between the valid and invalid regions of the input space. This is
an important step towards more automated robustness testing.Comment: 10 pages, conferenc
A "Piano Movers" Problem Reformulated
It has long been known that cylindrical algebraic decompositions (CADs) can
in theory be used for robot motion planning. However, in practice even the
simplest examples can be too complicated to tackle. We consider in detail a
"Piano Mover's Problem" which considers moving an infinitesimally thin piano
(or ladder) through a right-angled corridor.
Producing a CAD for the original formulation of this problem is still
infeasible after 25 years of improvements in both CAD theory and computer
hardware. We review some alternative formulations in the literature which use
differing levels of geometric analysis before input to a CAD algorithm. Simpler
formulations allow CAD to easily address the question of the existence of a
path. We provide a new formulation for which both a CAD can be constructed and
from which an actual path could be determined if one exists, and analyse the
CADs produced using this approach for variations of the problem.
This emphasises the importance of the precise formulation of such problems
for CAD. We analyse the formulations and their CADs considering a variety of
heuristics and general criteria, leading to conclusions about tackling other
problems of this form.Comment: 8 pages. Copyright IEEE 201
Constructing IGA-suitable planar parameterization from complex CAD boundary by domain partition and global/local optimization
In this paper, we propose a general framework for constructing IGA-suitable
planar B-spline parameterizations from given complex CAD boundaries consisting
of a set of B-spline curves. Instead of forming the computational domain by a
simple boundary, planar domains with high genus and more complex boundary
curves are considered. Firstly, some pre-processing operations including
B\'ezier extraction and subdivision are performed on each boundary curve in
order to generate a high-quality planar parameterization; then a robust planar
domain partition framework is proposed to construct high-quality patch-meshing
results with few singularities from the discrete boundary formed by connecting
the end points of the resulting boundary segments. After the topology
information generation of quadrilateral decomposition, the optimal placement of
interior B\'ezier curves corresponding to the interior edges of the
quadrangulation is constructed by a global optimization method to achieve a
patch-partition with high quality. Finally, after the imposition of
C1=G1-continuity constraints on the interface of neighboring B\'ezier patches
with respect to each quad in the quadrangulation, the high-quality B\'ezier
patch parameterization is obtained by a C1-constrained local optimization
method to achieve uniform and orthogonal iso-parametric structures while
keeping the continuity conditions between patches. The efficiency and
robustness of the proposed method are demonstrated by several examples which
are compared to results obtained by the skeleton-based parameterization
approach
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Non-Uniform Offsetting and its Applications in Laser Path Planning of Sterolithography Machine
Laser path planning is an important step in solid freeform fabrication processes such as
Stereolithography (SLA). An important consideration in the laser path planning is to compensate
the shape of laser beam. Currently the compensation is divided into two steps, Z-compensation
and X-Y compensation, and the shape of laser beam is assumed to be uniform for the whole
platform. In this research, we present a sampling based non-uniform offsetting method which
accounts for the different shapes of laser beam at various locations. We discuss the related steps
and algorithms. We demonstrate its effectiveness by using various test cases. Besides
improving the accuracy of SLA machine, non-uniform offsetting can also be applied to address
other accuracy issues caused by thermal and structural variationsMechanical Engineerin
Towards Automated Boundary Value Testing with Program Derivatives and Search
A natural and often used strategy when testing software is to use input
values at boundaries, i.e. where behavior is expected to change the most, an
approach often called boundary value testing or analysis (BVA). Even though
this has been a key testing idea for long it has been hard to clearly define
and formalize. Consequently, it has also been hard to automate.
In this research note we propose one such formalization of BVA by, in a
similar way as to how the derivative of a function is defined in mathematics,
considering (software) program derivatives. Critical to our definition is the
notion of distance between inputs and outputs which we can formalize and then
quantify based on ideas from Information theory.
However, for our (black-box) approach to be practical one must search for
test inputs with specific properties. Coupling it with search-based software
engineering is thus required and we discuss how program derivatives can be used
as and within fitness functions.
This brief note does not allow a deeper, empirical investigation but we use a
simple illustrative example throughout to introduce the main ideas. By
combining program derivatives with search, we thus propose a practical as well
as theoretically interesting technique for automated boundary value (analysis
and) testing
Influence of hand position on the near-effect in 3D attention
Voluntary reorienting of attention in real depth situations is characterized by an attentional bias to locations near the viewer once attention is deployed to a spatially cued object in depth. Previously this effect (initially referred to as the ‘near-effect’) was attributed to access of a 3D viewer-centred spatial representation for guiding attention in 3D space. The aim of this study was to investigate whether the near-bias could have been associated with the position of the response-hand, always near the viewer in previous studies investigating endogenous attentional shifts in real depth. In Experiment 1, the response-hand was placed at either the near or far target depth in a depth cueing task. Placing the response-hand at the far target depth abolished the near-effect, but failed to bias spatial attention to the far location. Experiment 2 showed that the response-hand effect was not modulated by the presence of an additional passive hand, whereas Experiment 3 confirmed that attentional prioritization of the passive hand was not masked by the influence of the responding hand on spatial attention in Experiment 2. The pattern of results is most consistent with the idea that response preparation can modulate spatial attention within a 3D viewer-centred spatial representation
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