272 research outputs found
An Adaptive Flow-Aware Packet Scheduling Algorithm for Multipath Tunnelling
This paper proposes AFMT, a packet scheduling algorithm to achieve adaptive
flow-aware multipath tunnelling. AFMT has two unique properties. Firstly, it
implements robust adaptive traffic splitting for the subtunnels. Secondly, it
detects and schedules bursts of packets cohesively, a scheme that already
enabled traffic splitting for load balancing with little to no packet
reordering.
Several NS-3 experiments over different network topologies show that AFMT
successfully deals with changing path characteristics due to background traffic
while increasing throughput and reliability.Comment: submitted and accepted on IEEE LCN 2019, 4 pages, 5 figure
Refining mutation variants in Cartesian genetic programming
In this work, we improve upon two frequently used mutation algorithms and therefore introduce three refined mutation strategies for Cartesian Genetic Programming. At first, we take the probabilistic concept of a mutation rate and split it into two mutation rates, one for active and inactive nodes respectively. Afterwards, the mutation method Single is taken and extended. Single mutates nodes until an active node is hit. Here, our extension mutates nodes until more than one but still predefined number n of active nodes are hit. At last, this concept is taken and a decay rate for n is introduced. Thus, we decrease the required number of active nodes hit per mutation step during CGP’s training process. We show empirically on different classification, regression and boolean regression benchmarks that all methods lead to better fitness values. This is then further supported by probabilistic comparison methods such as the Bayesian comparison of classifiers and the Mann-Whitney-U-Test. However, these improvements come with the cost of more mutation steps needed which in turn lengthens the training time. The third variant, in which n is decreased, does not differ from the second mutation strategy listed
SupRB: A Supervised Rule-based Learning System for Continuous Problems
We propose the SupRB learning system, a new Pittsburgh-style learning
classifier system (LCS) for supervised learning on multi-dimensional continuous
decision problems. SupRB learns an approximation of a quality function from
examples (consisting of situations, choices and associated qualities) and is
then able to make an optimal choice as well as predict the quality of a choice
in a given situation. One area of application for SupRB is parametrization of
industrial machinery. In this field, acceptance of the recommendations of
machine learning systems is highly reliant on operators' trust. While an
essential and much-researched ingredient for that trust is prediction quality,
it seems that this alone is not enough. At least as important is a
human-understandable explanation of the reasoning behind a recommendation.
While many state-of-the-art methods such as artificial neural networks fall
short of this, LCSs such as SupRB provide human-readable rules that can be
understood very easily. The prevalent LCSs are not directly applicable to this
problem as they lack support for continuous choices. This paper lays the
foundations for SupRB and shows its general applicability on a simplified model
of an additive manufacturing problem.Comment: Submitted to the Genetic and Evolutionary Computation Conference 2020
(GECCO 2020
Weighted mutation of connections to mitigate search space limitations in Cartesian Genetic Programming
This work presents and evaluates a novel modification to existing mutation operators for Cartesian Genetic Programming (CGP).
We discuss and highlight a so far unresearched limitation of how CGP explores its search space which is caused by certain nodes being inactive for long periods of time.
Our new mutation operator is intended to avoid this by associating each node with a dynamically changing weight. When mutating a connection between nodes, those weights are then used to bias the probability distribution in favour of inactive nodes.
This way, inactive nodes have a higher probability of becoming active again.
We include our mutation operator into two variants of CGP and benchmark both versions on four Boolean learning tasks.
We analyse the average numbers of iterations a node is inactive and show that our modification has the intended effect on node activity.
The influence of our modification on the number of iterations until a solution is reached is ambiguous if the same number of nodes is used as in the baseline without our modification.
However, our results show that our new mutation operator leads to fewer nodes being required for the same performance; this saves CPU time in each iteration
XCS Classifier System with Experience Replay
XCS constitutes the most deeply investigated classifier system today. It
bears strong potentials and comes with inherent capabilities for mastering a
variety of different learning tasks. Besides outstanding successes in various
classification and regression tasks, XCS also proved very effective in certain
multi-step environments from the domain of reinforcement learning. Especially
in the latter domain, recent advances have been mainly driven by algorithms
which model their policies based on deep neural networks -- among which the
Deep-Q-Network (DQN) is a prominent representative. Experience Replay (ER)
constitutes one of the crucial factors for the DQN's successes, since it
facilitates stabilized training of the neural network-based Q-function
approximators. Surprisingly, XCS barely takes advantage of similar mechanisms
that leverage stored raw experiences encountered so far. To bridge this gap,
this paper investigates the benefits of extending XCS with ER. On the one hand,
we demonstrate that for single-step tasks ER bears massive potential for
improvements in terms of sample efficiency. On the shady side, however, we
reveal that the use of ER might further aggravate well-studied issues not yet
solved for XCS when applied to sequential decision problems demanding for
long-action-chains
PDPK: A Framework to Synthesise Process Data and Corresponding Procedural Knowledge for Manufacturing
Procedural knowledge describes how to accomplish tasks and mitigate problems.
Such knowledge is commonly held by domain experts, e.g. operators in
manufacturing who adjust parameters to achieve quality targets. To the best of
our knowledge, no real-world datasets containing process data and corresponding
procedural knowledge are publicly available, possibly due to corporate
apprehensions regarding the loss of knowledge advances. Therefore, we provide a
framework to generate synthetic datasets that can be adapted to different
domains. The design choices are inspired by two real-world datasets of
procedural knowledge we have access to. Apart from containing representations
of procedural knowledge in Resource Description Framework (RDF)-compliant
knowledge graphs, the framework simulates parametrisation processes and
provides consistent process data. We compare established embedding methods on
the resulting knowledge graphs, detailing which out-of-the-box methods have the
potential to represent procedural knowledge. This provides a baseline which can
be used to increase the comparability of future work. Furthermore, we validate
the overall characteristics of a synthesised dataset by comparing the results
to those achievable on a real-world dataset. The framework and evaluation code,
as well as the dataset used in the evaluation, are available open source
A closer look at sum-based embeddings for knowledge graphs containing procedural knowledge
While knowledge graphs and their embedding into low dimensional vectors are established fields of research, they mostly cover factual knowledge. However, to improve downstream models, e. g. for predictive quality in real-world industrial use cases, embeddings of procedural knowledge, available in the form of rules, could be utilized. As such, we investigate which properties of embedding algorithms could prove beneficial in this scenario and evaluate which established embedding methodologies are suited to form the basis of sum-based embeddings of different representations of procedural knowledge
Forecasting of residential unit's heat demands: a comparison of machine learning techniques in a real-world case study
A large proportion of the energy consumed by private households is used for space heating and domestic hot water. In the context of the energy transition, the predominant aim is to reduce this consumption. In addition to implementing better energy standards in new buildings and refurbishing old buildings, intelligent energy management concepts can also contribute by operating heat generators according to demand based on an expected heat requirement. This requires forecasting models for heat demand to be as accurate and reliable as possible. In this paper, we present a case study of a newly built medium-sized living quarter in central Europe made up of 66 residential units from which we gathered consumption data for almost two years. Based on this data, we investigate the possibility of forecasting heat demand using a variety of time series models and offline and online machine learning (ML) techniques in a standard data science approach. We chose to analyze different modeling techniques as they can be used in different settings, where time series models require no additional data, offline ML needs a lot of data gathered up front, and online ML could be deployed from day one. A special focus lies on peak demand and outlier forecasting, as well as investigations into seasonal expert models. We also highlight the computational expense and explainability characteristics of the used models. We compare the used methods with naive models as well as each other, finding that time series models, as well as online ML, do not yield promising results. Accordingly, we will deploy one of the offline ML models in our real-world energy management system in the near future
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