3,608 research outputs found
Coordinating views for data visualisation and algorithmic profiling
A number of researchers have designed visualisation systems that consist of multiple components, through which data and interaction commands flow. Such multistage (hybrid) models can be used to reduce algorithmic complexity, and to open up intermediate stages of algorithms for inspection and steering. In this paper, we present work on aiding the developer and the user of such algorithms through the application of interactive visualisation techniques. We present a set of tools designed to profile the performance of other visualisation components, and provide further functionality for the exploration of high dimensional data sets. Case studies are provided, illustrating the application of the profiling modules to a number of data sets. Through this work we are exploring ways in which techniques traditionally used to prepare for visualisation runs, and to retrospectively analyse them, can find new uses within the context of a multi-component visualisation system
Dispelling the N^3 myth for the Kt jet-finder
At high-energy colliders, jets of hadrons are the observable counterparts of
the perturbative concepts of quarks and gluons. Good procedures for identifying
jets are central to experimental analyses and comparisons with theory. The Kt
family of successive recombination jet finders has been widely advocated
because of its conceptual simplicity and flexibility and its unique ability to
approximately reconstruct the partonic branching sequence in an event. Until
now however, it had been believed that for an ensemble of N particles the
algorithmic complexity of the Kt jet finder scaled as N^3, a severe issue in
the high multiplicity environments of LHC and heavy-ion colliders. We here show
that the computationally complex part of Kt jet-clustering can be reduced to
two-dimensional nearest neighbour location for a dynamic set of points.
Borrowing techniques developed for this extensively studied problem in
computational geometry, Kt jet-finding can then be performed in N ln N time.
Code based on these ideas is found to run faster than all other jet finders in
current use.Comment: 11 pages, 3 figures; v2, to appear in Phys.Lett.B, includes an extra
section briefly discussing the issues of jet areas and pileup subtraction,
and also the Cambridge/Aachen jet finde
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