1,978 research outputs found
Manycore processing of repeated range queries over massive moving objects observations
The ability to timely process significant amounts of continuously updated
spatial data is mandatory for an increasing number of applications. Parallelism
enables such applications to face this data-intensive challenge and allows the
devised systems to feature low latency and high scalability. In this paper we
focus on a specific data-intensive problem, concerning the repeated processing
of huge amounts of range queries over massive sets of moving objects, where the
spatial extents of queries and objects are continuously modified over time. To
tackle this problem and significantly accelerate query processing we devise a
hybrid CPU/GPU pipeline that compresses data output and save query processing
work. The devised system relies on an ad-hoc spatial index leading to a problem
decomposition that results in a set of independent data-parallel tasks. The
index is based on a point-region quadtree space decomposition and allows to
tackle effectively a broad range of spatial object distributions, even those
very skewed. Also, to deal with the architectural peculiarities and limitations
of the GPUs, we adopt non-trivial GPU data structures that avoid the need of
locked memory accesses and favour coalesced memory accesses, thus enhancing the
overall memory throughput. To the best of our knowledge this is the first work
that exploits GPUs to efficiently solve repeated range queries over massive
sets of continuously moving objects, characterized by highly skewed spatial
distributions. In comparison with state-of-the-art CPU-based implementations,
our method highlights significant speedups in the order of 14x-20x, depending
on the datasets, even when considering very cheap GPUs
Hysteresis in Adiabatic Dynamical Systems: an Introduction
We give a nontechnical description of the behaviour of dynamical systems
governed by two distinct time scales. We discuss in particular memory effects,
such as bifurcation delay and hysteresis, and comment the scaling behaviour of
hysteresis cycles. These properties are illustrated on a few simple examples.Comment: 28 pages, 10 ps figures, AMS-LaTeX. This is the introduction of my
Ph.D. dissertation, available at
http://dpwww.epfl.ch/instituts/ipt/berglund/these.htm
SwiftSpatial: Spatial Joins on Modern Hardware
Spatial joins are among the most time-consuming queries in spatial data
management systems. In this paper, we propose SwiftSpatial, a specialized
accelerator architecture tailored for spatial joins. SwiftSpatial contains
multiple high-performance join units with innovative hybrid parallelism,
several efficient memory management units, and an integrated on-chip join
scheduler. We prototype SwiftSpatial on an FPGA and incorporate the R-tree
synchronous traversal algorithm as the control flow. Benchmarked against
various CPU and GPU-based spatial data processing systems, SwiftSpatial
demonstrates a latency reduction of up to 5.36x relative to the best-performing
baseline, while requiring 6.16x less power. The remarkable performance and
energy efficiency of SwiftSpatial lay a solid foundation for its future
integration into spatial data management systems, both in data centers and at
the edge
Feat-SKSJ: Fast and Exact Algorithm for Top-k Spatial-Keyword Similarity Join
Due to the proliferation of GPS-enabled mobile devices and IoT environments, location-based services are generating a large number of objects that contain both spatial and keyword information, and spatial-keyword databases are receiving much attention. This paper addresses the problem of top-k spatial-keyword similarity join, which outputs k object pairs with the highest similarity. This query is a primitive operator for important applications, including duplicate detection, recommendation, and clustering. The main bottleneck of the top-k spatial-keyword similarity join is to compute the similarity of a given object pair. To avoid this computation as much as possible, a state-of-the-art algorithm utilizes a filter that can skip the exact similarity computation of a given pair. However, this algorithm suffers from a loose threshold at the first stage, a high filtering cost, and the impossibility of filtering many pairs in a batch. We propose Feat-SKSJ, which removes these drawbacks and quickly outputs the exact result. Extensive experiments on real datasets show that Feat-SKSJ is significantly faster than the state-of-the-art algorithm
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