241 research outputs found
TorchCP: A Library for Conformal Prediction based on PyTorch
TorchCP is a Python toolbox for conformal prediction research on deep
learning models. It contains various implementations for posthoc and training
methods for classification and regression tasks (including multi-dimension
output). TorchCP is built on PyTorch (Paszke et al., 2019) and leverages the
advantages of matrix computation to provide concise and efficient inference
implementations. The code is licensed under the LGPL license and is
open-sourced at
Shot noise of spin current and spin transfer torque
We report the theoretical investigation of noise spectrum of spin current and
spin transfer torque for non-colinear spin polarized transport in a spin-valve
device which consists of normal scattering region connected by two
ferromagnetic electrodes. Our theory was developed using non-equilibrium
Green's function method and general non-linear and
relations were derived as a function of angle between magnetization of
two leads. We have applied our theory to a quantum dot system with a resonant
level coupled with two ferromagnetic electrodes. It was found that for the MNM
system, the auto-correlation of spin current is enough to characterize the
fluctuation of spin current. For a system with three ferromagnetic layers,
however, both auto-correlation and cross-correlation of spin current are needed
to characterize the noise spectrum of spin current. Furthermore, the spin
transfer torque and the torque noise were studied for the MNM system. For a
quantum dot with a resonant level, the derivative of spin torque with respect
to bias voltage is proportional to when the system is far away
from the resonance. When the system is near the resonance, the spin transfer
torque becomes non-sinusoidal function of . The derivative of noise
spectrum of spin transfer torque with respect to the bias voltage
behaves differently when the system is near or far away from the resonance.
Specifically, the differential shot noise of spin transfer torque is a
concave function of near the resonance while it becomes convex
function of far away from resonance. For certain bias voltages, the
period becomes instead of . For small , it
was found that the differential shot noise of spin transfer torque is very
sensitive to the bias voltage and the other system parameters.Comment: 15pages, 6figure
Does Confidence Calibration Help Conformal Prediction?
Conformal prediction, as an emerging uncertainty qualification technique,
constructs prediction sets that are guaranteed to contain the true label with
high probability. Previous works usually employ temperature scaling to
calibrate the classifier, assuming that confidence calibration can benefit
conformal prediction. In this work, we first show that post-hoc calibration
methods surprisingly lead to larger prediction sets with improved calibration,
while over-confidence with small temperatures benefits the conformal prediction
performance instead. Theoretically, we prove that high confidence reduces the
probability of appending a new class in the prediction set. Inspired by the
analysis, we propose a novel method,
(ConfTS), which rectifies the objective through the gap between the threshold
and the non-conformity score of the ground-truth label. In this way, the new
objective of ConfTS will optimize the temperature value toward an optimal set
that satisfies the . Experiments demonstrate that
our method can effectively improve widely-used conformal prediction methods
In Defense of Softmax Parametrization for Calibrated and Consistent Learning to Defer
Enabling machine learning classifiers to defer their decision to a downstream
expert when the expert is more accurate will ensure improved safety and
performance. This objective can be achieved with the learning-to-defer
framework which aims to jointly learn how to classify and how to defer to the
expert. In recent studies, it has been theoretically shown that popular
estimators for learning to defer parameterized with softmax provide unbounded
estimates for the likelihood of deferring which makes them uncalibrated.
However, it remains unknown whether this is due to the widely used softmax
parameterization and if we can find a softmax-based estimator that is both
statistically consistent and possesses a valid probability estimator. In this
work, we first show that the cause of the miscalibrated and unbounded estimator
in prior literature is due to the symmetric nature of the surrogate losses used
and not due to softmax. We then propose a novel statistically consistent
asymmetric softmax-based surrogate loss that can produce valid estimates
without the issue of unboundedness. We further analyze the non-asymptotic
properties of our method and empirically validate its performance and
calibration on benchmark datasets.Comment: NeurIPS 202
On the Importance of Feature Separability in Predicting Out-Of-Distribution Error
Estimating the generalization performance is practically challenging on
out-of-distribution (OOD) data without ground truth labels. While previous
methods emphasize the connection between distribution difference and OOD
accuracy, we show that a large domain gap not necessarily leads to a low test
accuracy. In this paper, we investigate this problem from the perspective of
feature separability, and propose a dataset-level score based upon feature
dispersion to estimate the test accuracy under distribution shift. Our method
is inspired by desirable properties of features in representation learning:
high inter-class dispersion and high intra-class compactness. Our analysis
shows that inter-class dispersion is strongly correlated with the model
accuracy, while intra-class compactness does not reflect the generalization
performance on OOD data. Extensive experiments demonstrate the superiority of
our method in both prediction performance and computational efficiency
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