18 research outputs found
On k-enclosing objects in a coloured point set
We introduce the exact coloured
k
-enclosing object
problem: given a set
P
of
n
points in
R
2
, each of
which has an associated colour in
f
1
;:::;t
g
, and a vec-
tor
c
= (
c
1
;:::;c
t
), where
c
i
2
Z
+
for each 1
i
t
,
nd a region that contains exactly
c
i
points of
P
of
colour
i
for each
i
. We examine the problems of nd-
ing exact coloured
k
-enclosing axis-aligned rectangles,
squares, discs, and two-sided dominating regions in a
t
-coloured point setPostprint (published version
Output-Sensitive Tools for Range Searching in Higher Dimensions
Let be a set of points in . A point is
\emph{-shallow} if it lies in a halfspace which contains at most points
of (including ). We show that if all points of are -shallow, then
can be partitioned into subsets, so that any hyperplane
crosses at most subsets. Given such
a partition, we can apply the standard construction of a spanning tree with
small crossing number within each subset, to obtain a spanning tree for the
point set , with crossing number . This allows us to extend the construction of Har-Peled
and Sharir \cite{hs11} to three and higher dimensions, to obtain, for any set
of points in (without the shallowness assumption), a
spanning tree with {\em small relative crossing number}. That is, any
hyperplane which contains points of on one side, crosses
edges of . Using a
similar mechanism, we also obtain a data structure for halfspace range
counting, which uses space (and somewhat higher
preprocessing cost), and answers a query in time , where is the output size
Data-Centric Distrust Quantification for Responsible AI: When Data-driven Outcomes Are Not Reliable
At the same time that AI and machine learning are becoming central to human
life, their potential harms become more vivid. In the presence of such
drawbacks, a critical question one needs to address before using these
data-driven technologies to make a decision is whether to trust their outcomes.
Aligned with recent efforts on data-centric AI, this paper proposes a novel
approach to address the trust question through the lens of data, by associating
data sets with distrust quantification that specify their scope of use for
predicting future query points. The distrust values raise warning signals when
a prediction based on a dataset is questionable and are valuable alongside
other techniques for trustworthy AI. We propose novel algorithms for computing
the distrust values in the neighborhood of a query point efficiently and
effectively. Learning the necessary components of the measures from the data
itself, our sub-linear algorithms scale to very large and multi-dimensional
settings. Besides demonstrating the efficiency of our algorithms, our extensive
experiments reflect a consistent correlation between distrust values and model
performance. This underscores the message that when the distrust value of a
query point is high, the prediction outcome should be discarded or at least not
considered for critical decisions
Complete Classification and Efficient Determination of Arrangements Formed by Two Ellipsoids
International audienceArrangements of geometric objects refer to the spatial partitions formed by the objects and they serve as an underlining structure of motion design, analysis and planning in CAD/CAM, robotics, molecular modeling, manufacturing and computer-assisted radio-surgery. Arrangements are especially useful to collision detection, which is a key task in various applications such as computer animation , virtual reality, computer games, robotics, CAD/CAM and computational physics. Ellipsoids are commonly used as bounding volumes in approximating complex geometric objects in collision detection. In this paper we present an in-depth study on the arrangements formed by two ellipsoids. Specifically, we present a classification of these arrangements and propose an efficient algorithm for determining the arrangement formed by any particular pair of ellipsoids. A stratification diagram is also established to show the connections among all the arrangements formed by two ellipsoids. Our results for the first time elucidate all possible relative positions between two arbitrary ellipsoids and provides an efficient and robust algorithm for determining the relative position of any two given ellipsoids, therefore providing the necessary foundation for developing practical and trustworthy methods for processing ellipsoids for collision analysis or simulation in various applications