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Stereo Frustums: A Siamese Pipeline for 3D Object Detection

arXiv.org Artificial Intelligence

The paper proposes a light-weighted stereo frustums matching module for 3D objection detection. The proposed framework takes advantage of a high-performance 2D detector and a point cloud segmentation network to regress 3D bounding boxes for autonomous driving vehicles. Instead of performing traditional stereo matching to compute disparities, the module directly takes the 2D proposals from both the left and the right views as input. Based on the epipolar constraints recovered from the well-calibrated stereo cameras, we propose four matching algorithms to search for the best match for each proposal between the stereo image pairs. Each matching pair proposes a segmentation of the scene which is then fed into a 3D bounding box regression network. Results of extensive experiments on KITTI dataset demonstrate that the proposed Siamese pipeline outperforms the state-of-the-art stereo-based 3D bounding box regression methods.


On the Privacy Risks of Algorithmic Fairness

arXiv.org Machine Learning

Algorithmic fairness and privacy are essential elements of trustworthy machine learning for critical decision making processes. Fair machine learning algorithms are developed to minimize discrimination against protected groups in machine learning. This is achieved, for example, by imposing a constraint on the model to equalize its behavior across different groups. This can significantly increase the influence of some training data points on the fair model. We study how this change in influence can change the information leakage of the model about its training data. We analyze the privacy risks of statistical notions of fairness (i.e., equalized odds) through the lens of membership inference attacks: inferring whether a data point was used for training a model. We show that fairness comes at the cost of privacy. However, this privacy cost is not distributed equally: the information leakage of fair models increases significantly on the unprivileged subgroups, which suffer from the discrimination in regular models. Furthermore, the more biased the underlying data is, the higher the privacy cost of achieving fairness for the unprivileged subgroups is. We demonstrate this effect on multiple datasets and explain how fairness-aware learning impacts privacy.


(Visually) Interpreting the confusion-matrix:

#artificialintelligence

But first, what is a confusion matrix? In machine learning, a confusion matrix is a kind-of confusing table used to understand how well our model predictions perform(especially confusing when we have multiple classes and not the classic binary 0/1 problems). However, gradually I figured out that the confusion-matrix is not so confusing and helps me a ton in understanding the model behaviour and interpreting the results. So I'm going to try to do the same here.. make it less confusing, more interesting and easier to interpret! The columns represent predictions made by our model and the rows represent the actual classes(this is the format of the very popular Python library for ML: sklearn.


New Artificial Intelligence Tool Improves Breast Cancer Detection on Mammography

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The upper panels show the craniocaudal and the mediolateral oblique views. The lower panels show a close-up of the left breast area containing the lesion. The case is one of the false-negative cases included in the dataset. Accordingly, the initial screening assessment was a BI-RADS 2, meaning visible findings were judged as benign. After 1 year, the patient presented for another screening examination.


Efficient Permutation Discovery in Causal DAGs

arXiv.org Machine Learning

The problem of learning a directed acyclic graph (DAG) up to Markov equivalence is equivalent to the problem of finding a permutation of the variables that induces the sparsest graph. Without additional assumptions, this task is known to be NP-hard. Building on the minimum degree algorithm for sparse Cholesky decomposition, but utilizing DAG-specific problem structure, we introduce an efficient algorithm for finding such sparse permutations. We show that on jointly Gaussian distributions, our method with depth $w$ runs in $O(p^{w+3})$ time. We compare our method with $w = 1$ to algorithms for finding sparse elimination orderings of undirected graphs, and show that taking advantage of DAG-specific problem structure leads to a significant improvement in the discovered permutation. We also compare our algorithm to provably consistent causal structure learning algorithms, such as the PC algorithm, GES, and GSP, and show that our method achieves comparable performance with a shorter runtime. Thus, our method can be used on its own for causal structure discovery. Finally, we show that there exist dense graphs on which our method achieves almost perfect performance, so that unlike most existing causal structure learning algorithms, the situations in which our algorithm achieves both good performance and good runtime are not limited to sparse graphs.


Ridge Regression with Frequent Directions: Statistical and Optimization Perspectives

arXiv.org Machine Learning

Despite its impressive theory \& practical performance, Frequent Directions (\acrshort{fd}) has not been widely adopted for large-scale regression tasks. Prior work has shown randomized sketches (i) perform worse in estimating the covariance matrix of the data than \acrshort{fd}; (ii) incur high error when estimating the bias and/or variance on sketched ridge regression. We give the first constant factor relative error bounds on the bias \& variance for sketched ridge regression using \acrshort{fd}. We complement these statistical results by showing that \acrshort{fd} can be used in the optimization setting through an iterative scheme which yields high-accuracy solutions. This improves on randomized approaches which need to compromise the need for a new sketch every iteration with speed of convergence. In both settings, we also show using \emph{Robust Frequent Directions} further enhances performance.


Selective Classification via One-Sided Prediction

arXiv.org Machine Learning

We propose a novel method for selective classification (SC), a problem which allows a classifier to abstain from predicting some instances, thus trading off accuracy against coverage (the fraction of instances predicted). In contrast to prior gating or confidence-set based work, our proposed method optimises a collection of class-wise decoupled one-sided empirical risks, and is in essence a method for explicitly finding the largest decision sets for each class that have few false positives. This one-sided prediction (OSP) based relaxation yields an SC scheme that attains near-optimal coverage in the practically relevant high target accuracy regime, and further admits efficient implementation, leading to a flexible and principled method for SC. We theoretically derive generalization bounds for SC and OSP, and empirically we show that our scheme strongly outperforms state of the art methods in coverage at small error levels.


Acoustics Based Intent Recognition Using Discovered Phonetic Units for Low Resource Languages

arXiv.org Artificial Intelligence

With recent advancements in language technologies, humansare now interacting with technology through speech. To in-crease the reach of these technologies, we need to build suchsystems in local languages. A major bottleneck here are theunderlying data-intensive parts that make up such systems,including automatic speech recognition (ASR) systems thatrequire large amounts of labelled data. With the aim of aidingdevelopment of dialog systems in low resourced languages,we propose a novel acoustics based intent recognition systemthat uses discovered phonetic units for intent classification.The system is made up of two blocks - the first block gen-erates a transcript of discovered phonetic units for the inputaudio, and the second block which performs intent classifi-cation from the generated phonemic transcripts. Our workpresents results for such a system for two languages families- Indic languages and Romance languages, for two differentintent recognition tasks. We also perform multilingual train-ing of our intent classifier and show improved cross-lingualtransfer and performance on an unknown language with zeroresources in the same language family.


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FDA: Antigen tests for COVID-19 are rapid but can lead to false positives

Boston Herald

The U.S. Food and Drug Administration is alerting clinical laboratory staff and health care providers that false positive results can occur with antigen tests for the virus that causes COVID-19. In a letter to stakeholders, the FDA said Tuesday that while antigen tests can be used for the rapid detection of SARS-CoV-2, false positive results can occur, especially if users don't follow the instructions. "The FDA is aware of reports of false positive results associated with antigen tests used in nursing homes and other settings and continues to monitor and evaluate these reports and other available information about device safety and performance," the letter said. A Boston-area infectious disease expert said the antigen tests are good for large scale screening, when used properly, but must be followed up with more accurate testing. "If you are testing a population at low risk, it's fine to do these tests for screening," said Dr. Daniel Kuritzkes, chief of the Division of Infectious Diseases at Brigham and Women's Hospital.