23 research outputs found
Ranking and significance of variable-length similarity-based time series motifs
The detection of very similar patterns in a time series, commonly called
motifs, has received continuous and increasing attention from diverse
scientific communities. In particular, recent approaches for discovering
similar motifs of different lengths have been proposed. In this work, we show
that such variable-length similarity-based motifs cannot be directly compared,
and hence ranked, by their normalized dissimilarities. Specifically, we find
that length-normalized motif dissimilarities still have intrinsic dependencies
on the motif length, and that lowest dissimilarities are particularly affected
by this dependency. Moreover, we find that such dependencies are generally
non-linear and change with the considered data set and dissimilarity measure.
Based on these findings, we propose a solution to rank those motifs and measure
their significance. This solution relies on a compact but accurate model of the
dissimilarity space, using a beta distribution with three parameters that
depend on the motif length in a non-linear way. We believe the incomparability
of variable-length dissimilarities could go beyond the field of time series,
and that similar modeling strategies as the one used here could be of help in a
more broad context.Comment: 20 pages, 10 figure
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Temporal pattern recognition in video clips detection
Temporal representation and reasoning plays an important role in Data Mining and Knowledge Discovery, particularly, in mining and recognizing patterns with rich temporal information. Based on a formal characterization of time-series and state-sequences, this paper presents the computational technique and algorithm for matching state-based temporal patterns. As a case study of real-life applications, zone-defense pattern recognition in basketball games is specially examined as an illustrating example. Experimental results demonstrate that it provides a formal and comprehensive temporal ontology for research and applications in video events detection
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The Swiss army knife of time series data mining: ten useful things you can do with the matrix profile and ten lines of code
Efficiency Optimisation of a Forestry Crane by Implement Hydraulics with Energy Recovery
Forwarders are an essential part in fully mechanised timber harvesting chains. Due to a
suboptimal energy usage at the implement hydraulics, caused by unused energy recovery,
there is a great potential for an optimisation of the machines to increase its sustainability and
environmental compatibility. Hence, innovative solutions for this challenge are designed
within the project ‘Forwarder2020’ at the Karlsruhe Institute of Technology (KIT), embedded
in and sponsored by the European program ‘Horizon 2020’, managed by the project leader
HSM Hohenloher Spezial-Maschinenbau GmbH & Co. KG.
The focus in this treatise is on the energy efficiency of a forestry crane, for example mounted
on a forwarder. On current machines there is no built-in system to recover energy. An energy
recuperation and regeneration system is therefore developed for forestry cranes.
To compare the efficiency of different machines or system architectures and to evaluate the
energy recovery potential of loading processes, reference loading cycles have been established
based on field measurements of real logging processes. These standardized reference
cycles represent recurrent loading cycles in a working environment
NATSA: A Near-Data Processing Accelerator for Time Series Analysis
Time series analysis is a key technique for extracting and predicting events
in domains as diverse as epidemiology, genomics, neuroscience, environmental
sciences, economics, and more. Matrix profile, the state-of-the-art algorithm
to perform time series analysis, computes the most similar subsequence for a
given query subsequence within a sliced time series. Matrix profile has low
arithmetic intensity, but it typically operates on large amounts of time series
data. In current computing systems, this data needs to be moved between the
off-chip memory units and the on-chip computation units for performing matrix
profile. This causes a major performance bottleneck as data movement is
extremely costly in terms of both execution time and energy.
In this work, we present NATSA, the first Near-Data Processing accelerator
for time series analysis. The key idea is to exploit modern 3D-stacked High
Bandwidth Memory (HBM) to enable efficient and fast specialized matrix profile
computation near memory, where time series data resides. NATSA provides three
key benefits: 1) quickly computing the matrix profile for a wide range of
applications by building specialized energy-efficient floating-point arithmetic
processing units close to HBM, 2) improving the energy efficiency and execution
time by reducing the need for data movement over slow and energy-hungry buses
between the computation units and the memory units, and 3) analyzing time
series data at scale by exploiting low-latency, high-bandwidth, and
energy-efficient memory access provided by HBM. Our experimental evaluation
shows that NATSA improves performance by up to 14.2x (9.9x on average) and
reduces energy by up to 27.2x (19.4x on average), over the state-of-the-art
multi-core implementation. NATSA also improves performance by 6.3x and reduces
energy by 10.2x over a general-purpose NDP platform with 64 in-order cores.Comment: To appear in the 38th IEEE International Conference on Computer
Design (ICCD 2020