173,204 research outputs found
Input Prioritization for Testing Neural Networks
Deep neural networks (DNNs) are increasingly being adopted for sensing and
control functions in a variety of safety and mission-critical systems such as
self-driving cars, autonomous air vehicles, medical diagnostics, and industrial
robotics. Failures of such systems can lead to loss of life or property, which
necessitates stringent verification and validation for providing high
assurance. Though formal verification approaches are being investigated,
testing remains the primary technique for assessing the dependability of such
systems. Due to the nature of the tasks handled by DNNs, the cost of obtaining
test oracle data---the expected output, a.k.a. label, for a given input---is
high, which significantly impacts the amount and quality of testing that can be
performed. Thus, prioritizing input data for testing DNNs in meaningful ways to
reduce the cost of labeling can go a long way in increasing testing efficacy.
This paper proposes using gauges of the DNN's sentiment derived from the
computation performed by the model, as a means to identify inputs that are
likely to reveal weaknesses. We empirically assessed the efficacy of three such
sentiment measures for prioritization---confidence, uncertainty, and
surprise---and compare their effectiveness in terms of their fault-revealing
capability and retraining effectiveness. The results indicate that sentiment
measures can effectively flag inputs that expose unacceptable DNN behavior. For
MNIST models, the average percentage of inputs correctly flagged ranged from
88% to 94.8%
Comparison of Observed Galaxy Properties with Semianalytic Model Predictions using Machine Learning
With current and upcoming experiments such as WFIRST, Euclid and LSST, we can
observe up to billions of galaxies. While such surveys cannot obtain spectra
for all observed galaxies, they produce galaxy magnitudes in color filters.
This data set behaves like a high-dimensional nonlinear surface, an excellent
target for machine learning. In this work, we use a lightcone of semianalytic
galaxies tuned to match CANDELS observations from Lu et al. (2014) to train a
set of neural networks on a set of galaxy physical properties. We add realistic
photometric noise and use trained neural networks to predict stellar masses and
average star formation rates on real CANDELS galaxies, comparing our
predictions to SED fitting results. On semianalytic galaxies, we are nearly
competitive with template-fitting methods, with biases of dex for
stellar mass, dex for star formation rate, and dex for
metallicity. For the observed CANDELS data, our results are consistent with
template fits on the same data at dex bias in and
dex bias in star formation rate. Some of the bias is driven by SED-fitting
limitations, rather than limitations on the training set, and some is intrinsic
to the neural network method. Further errors are likely caused by differences
in noise properties between the semianalytic catalogs and data. Our results
show that galaxy physical properties can in principle be measured with neural
networks at a competitive degree of accuracy and precision to template-fitting
methods.Comment: 19 pages, 10 figures, 6 tables. Accepted for publication in Ap
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