6,596 research outputs found
Model Extraction Warning in MLaaS Paradigm
Cloud vendors are increasingly offering machine learning services as part of
their platform and services portfolios. These services enable the deployment of
machine learning models on the cloud that are offered on a pay-per-query basis
to application developers and end users. However recent work has shown that the
hosted models are susceptible to extraction attacks. Adversaries may launch
queries to steal the model and compromise future query payments or privacy of
the training data. In this work, we present a cloud-based extraction monitor
that can quantify the extraction status of models by observing the query and
response streams of both individual and colluding adversarial users. We present
a novel technique that uses information gain to measure the model learning rate
by users with increasing number of queries. Additionally, we present an
alternate technique that maintains intelligent query summaries to measure the
learning rate relative to the coverage of the input feature space in the
presence of collusion. Both these approaches have low computational overhead
and can easily be offered as services to model owners to warn them of possible
extraction attacks from adversaries. We present performance results for these
approaches for decision tree models deployed on BigML MLaaS platform, using
open source datasets and different adversarial attack strategies
Matter Wave Scattering from Ultracold Atoms in an Optical Lattice
We study matter wave scattering from an ultracold, many body atomic system
trapped in an optical lattice. We determine the angular cross section that a
matter wave probe sees and show that it is strongly affected by the many body
phase, superfluid or Mott insulator, of the target lattice. We determine these
cross sections analytically in the first Born approximation, and we examine the
variation at intermediate points in the phase transition by numerically
diagonalizing the Bose Hubbard Hamiltonian for a small lattice. We show that
matter wave scattering offers a convenient method for non-destructively probing
the quantum many body phase transition of atoms in an optical lattice.Comment: 4 pages, 2 figure
Dynamical trapping and chaotic scattering of the harmonically driven barrier
A detailed analysis of the classical nonlinear dynamics of a single driven
square potential barrier with harmonically oscillating position is performed.
The system exhibits dynamical trapping which is associated with the existence
of a stable island in phase space. Due to the unstable periodic orbits of the
KAM-structure, the driven barrier is a chaotic scatterer and shows stickiness
of scattering trajectories in the vicinity of the stable island. The
transmission function of a suitably prepared ensemble yields results which are
very similar to tunneling resonances in the quantum mechanical regime. However,
the origin of these resonances is different in the classical regime.Comment: 14 page
An Extended Empirical Saddlepoint Approximation for Intractable Likelihoods
The challenges posed by complex stochastic models used in computational
ecology, biology and genetics have stimulated the development of approximate
approaches to statistical inference. Here we focus on Synthetic Likelihood
(SL), a procedure that reduces the observed and simulated data to a set of
summary statistics, and quantifies the discrepancy between them through a
synthetic likelihood function. SL requires little tuning, but it relies on the
approximate normality of the summary statistics. We relax this assumption by
proposing a novel, more flexible, density estimator: the Extended Empirical
Saddlepoint approximation. In addition to proving the consistency of SL, under
either the new or the Gaussian density estimator, we illustrate the method
using two examples. One of these is a complex individual-based forest model for
which SL offers one of the few practical possibilities for statistical
inference. The examples show that the new density estimator is able to capture
large departures from normality, while being scalable to high dimensions, and
this in turn leads to more accurate parameter estimates, relative to the
Gaussian alternative. The new density estimator is implemented by the esaddle R
package, which can be found on the Comprehensive R Archive Network (CRAN)
Structure of multicorrelation sequences with integer part polynomial iterates along primes
Let be a measure preserving -action on the probability
space
vector polynomials, and . For any
and multicorrelation sequences of the form
we show that there exists a nilsequence
for which and This result simultaneously generalizes previous
results of Frantzikinakis [2] and the authors [11,13].Comment: 7 page
Partial Clustering in Binary Two-Dimensional Colloidal Suspensions
Strongly interacting binary mixtures of superparamagnetic colloidal particles
confined to a two-dimensional water-air interface are examined by theory,
computer simulation and experiment. The mixture exhibits a partial clustering
in equilibrium: in the voids of the matrix of unclustered big particles, the
small particles form subclusters with a sponge-like topology which is
accompanied by a characteristic small-wave vector peak in the small-small
structure factor. This partial clustering is a general phenomenon occurring for
strongly coupled negatively non-additive mixtures.Comment: 12 pages, 5 figures, submitted 200
Learning Multiple Defaults for Machine Learning Algorithms
The performance of modern machine learning methods highly depends on their
hyperparameter configurations. One simple way of selecting a configuration is
to use default settings, often proposed along with the publication and
implementation of a new algorithm. Those default values are usually chosen in
an ad-hoc manner to work good enough on a wide variety of datasets. To address
this problem, different automatic hyperparameter configuration algorithms have
been proposed, which select an optimal configuration per dataset. This
principled approach usually improves performance, but adds additional
algorithmic complexity and computational costs to the training procedure. As an
alternative to this, we propose learning a set of complementary default values
from a large database of prior empirical results. Selecting an appropriate
configuration on a new dataset then requires only a simple, efficient and
embarrassingly parallel search over this set. We demonstrate the effectiveness
and efficiency of the approach we propose in comparison to random search and
Bayesian Optimization
- …