13,817 research outputs found
Reducing Offline Evaluation Bias in Recommendation Systems
Recommendation systems have been integrated into the majority of large online
systems. They tailor those systems to individual users by filtering and ranking
information according to user profiles. This adaptation process influences the
way users interact with the system and, as a consequence, increases the
difficulty of evaluating a recommendation algorithm with historical data (via
offline evaluation). This paper analyses this evaluation bias and proposes a
simple item weighting solution that reduces its impact. The efficiency of the
proposed solution is evaluated on real world data extracted from Viadeo
professional social network.Comment: 23rd annual Belgian-Dutch Conference on Machine Learning (Benelearn
2014), Bruxelles : Belgium (2014
Using the Mean Absolute Percentage Error for Regression Models
We study in this paper the consequences of using the Mean Absolute Percentage
Error (MAPE) as a measure of quality for regression models. We show that
finding the best model under the MAPE is equivalent to doing weighted Mean
Absolute Error (MAE) regression. We show that universal consistency of
Empirical Risk Minimization remains possible using the MAPE instead of the MAE.Comment: European Symposium on Artificial Neural Networks, Computational
Intelligence and Machine Learning (ESANN), Apr 2015, Bruges, Belgium. 2015,
Proceedings of the 23-th European Symposium on Artificial Neural Networks,
Computational Intelligence and Machine Learning (ESANN 2015
Reducing offline evaluation bias of collaborative filtering algorithms
Recommendation systems have been integrated into the majority of large online
systems to filter and rank information according to user profiles. It thus
influences the way users interact with the system and, as a consequence, bias
the evaluation of the performance of a recommendation algorithm computed using
historical data (via offline evaluation). This paper presents a new application
of a weighted offline evaluation to reduce this bias for collaborative
filtering algorithms.Comment: European Symposium on Artificial Neural Networks, Computational
Intelligence and Machine Learning (ESANN), Apr 2015, Bruges, Belgium.
pp.137-142, 2015, Proceedings of the 23-th European Symposium on Artificial
Neural Networks, Computational Intelligence and Machine Learning (ESANN 2015
Identification of parameters in amplitude equations describing coupled wakes
We study the flow behind an array of equally spaced parallel cylinders. A
system of Stuart-Landau equations with complex parameters is used to model the
oscillating wakes. Our purpose is to identify the 6 scalar parameters which
most accurately reproduce the experimental data of Chauve and Le Gal [{Physica
D {\bf 58}}, pp 407--413, (1992)]. To do so, we perform a computational search
for the minimum of a distance \calj. We define \calj as the sum-square
difference of the data and amplitudes reconstructed using coupled equations.
The search algorithm is made more efficient through the use of a partially
analytical expression for the gradient . Indeed
can be obtained by the integration of a dynamical system propagating backwards
in time (a backpropagation equation for the Lagrange multipliers). Using the
parameters computed via the backpropagation method, the coupled Stuart-Landau
equations accurately predicted the experimental data from Chauve and Le Gal
over a correlation time of the system. Our method turns out to be quite robust
as evidenced by using noisy synthetic data obtained from integrations of the
coupled Stuart-Landau equations. However, a difficulty remains with
experimental data: in that case the several sets of identified parameters are
shown to yield equivalent predictions. This is due to a strong discretization
or ``round-off" error arising from the digitalization of the video images in
the experiment. This ambiguity in parameter identification has been reproduced
with synthetic data subjected to the same kind of discretization.Comment: 25 pages uuencoded compressed PostScript file (58K) with 13 figures
(155K in separated file) Submitted to Physica
Consistance de la minimisation du risque empirique pour l'optimisation de l'erreur relative moyenne
National audienceWe study in this paper the consequences of using the Mean Absolute Percentage Error (MAPE) as a measure of quality for regression models. We show that finding the best model under the MAPE is equivalent to doing weighted Mean Absolute Error (MAE) regression. We also show that, under some asumptions, universal consistency of Empirical Risk Minimization remains possible using the MAPE.Nous nous intéressons au problème de la minimisation de l'erreur relative moyenne dans le cadre des modèles de régression. Nous montrons que l'optimisation de ce critère est équivalente à la minimisation de l'erreur absolue par régressions pondérées et que l'approche par minimisation du risque empirique est, sous certaines hypothèses, consistante pour la minimisation de ce critère
On the three-dimensional temporal spectrum of stretched vortices
The three-dimensional stability problem of a stretched stationary vortex is
addressed in this letter. More specifically, we prove that the discrete part of
the temporal spectrum is only associated with two-dimensional perturbations.Comment: 4 pages, RevTeX, submitted to PR
Stopping power of hot QCD plasma
The partonic energy loss has been calculated taking both the hard and soft
contributions for all the processes, revealing the importance of the
individual channels. Cancellation of the intermediate separation scale has been
exhibited. Subtleties related to the identical final state partons have
properly been taken into account. The estimated collisional loss is compared
with its radiative counter part. We show that there exists a critical energy
() below which the collisional loss is more than its radiative
counterpart. In addition, we present closed form formulas for both the
collision probabilities and the stopping power ()Comment: revised version, section added, 9pages with 5 figure
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