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 Chapman, David


Interpretable Measurement of CNN Deep Feature Density using Copula and the Generalized Characteristic Function

arXiv.org Artificial Intelligence

We present a novel empirical approach toward measuring the Probability Density Function (PDF) of the deep features of Convolutional Neural Networks (CNNs). Measurement of the deep feature PDF is a valuable problem for several reasons. Notably, a. Understanding the deep feature PDF yields new insight into deep representations. b. Feature density methods are important for tasks such as anomaly detection which can improve the robustness of deep learning models in the wild. Interpretable measurement of the deep feature PDF is challenging due to the Curse of Dimensionality (CoD), and the Spatial intuition Limitation. Our novel measurement technique combines copula analysis with the Method of Orthogonal Moments (MOM), in order to directly measure the Generalized Characteristic Function (GCF) of the multivariate deep feature PDF. We find that, surprisingly, the one-dimensional marginals of non-negative deep CNN features after major blocks are not well approximated by a Gaussian distribution, and that these features increasingly approximate an exponential distribution with increasing network depth. Furthermore, we observe that deep features become increasingly independent with increasing network depth within their typical ranges. However, we surprisingly also observe that many deep features exhibit strong dependence (either correlation or anti-correlation) with other extremely strong detections, even if these features are independent within typical ranges. We elaborate on these findings in our discussion, where we propose a new hypothesis that exponentially infrequent large valued features correspond to strong computer vision detections of semantic targets, which would imply that these large-valued features are not outliers but rather an important detection signal.


Semi-supervised Contrastive Outlier removal for Pseudo Expectation Maximization (SCOPE)

arXiv.org Artificial Intelligence

Semi-supervised learning is the problem of training an accurate predictive model by combining a small labeled dataset with a presumably much larger unlabeled dataset. Many methods for semi-supervised deep learning have been developed, including pseudolabeling, consistency regularization, and contrastive learning techniques. Pseudolabeling methods however are highly susceptible to confounding, in which erroneous pseudolabels are assumed to be true labels in early iterations, thereby causing the model to reinforce its prior biases and thereby fail to generalize to strong predictive performance. We present a new approach to suppress confounding errors through a method we describe as Semi-supervised Contrastive Outlier removal for Pseudo Expectation Maximization (SCOPE). Like basic pseudolabeling, SCOPE is related to Expectation Maximization (EM), a latent variable framework which can be extended toward understanding cluster-assumption deep semi-supervised algorithms. However, unlike basic pseudolabeling which fails to adequately take into account the probability of the unlabeled samples given the model, SCOPE introduces an outlier suppression term designed to improve the behavior of EM iteration given a discrimination DNN backbone in the presence of outliers. Our results show that SCOPE greatly improves semi-supervised classification accuracy over a baseline, and furthermore when combined with consistency regularization achieves the highest reported accuracy for the semi-supervised CIFAR-10 classification task using 250 and 4000 labeled samples. Moreover, we show that SCOPE reduces the prevalence of confounding errors during pseudolabeling iterations by pruning erroneous high-confidence pseudolabeled samples that would otherwise contaminate the labeled set in subsequent retraining iterations.


RFC-Net: Learning High Resolution Global Features for Medical Image Segmentation on a Computational Budget

arXiv.org Artificial Intelligence

Learning High-Resolution representations is essential for semantic segmentation. Convolutional neural network (CNN)architectures with downstream and upstream propagation flow are popular for segmentation in medical diagnosis. However, due to performing spatial downsampling and upsampling in multiple stages, information loss is inexorable. On the contrary, connecting layers densely on high spatial resolution is computationally expensive. In this work, we devise a Loose Dense Connection Strategy to connect neurons in subsequent layers with reduced parameters. On top of that, using a m-way Tree structure for feature propagation we propose Receptive Field Chain Network (RFC-Net) that learns high resolution global features on a compressed computational space. Our experiments demonstrates that RFC-Net achieves state-of-the-art performance on Kvasir and CVC-ClinicDB benchmarks for Polyp segmentation.


Learning to See Where and What: Training a Net to Make Saccades and Recognize Handwritten Characters

Neural Information Processing Systems

This paper describes an approach to integrated segmentation and recognition of hand-printed characters. The approach, called Saccade, integrates ballistic and corrective saccades (eye movements) with character recognition. A single backpropagation net is trained to make a classification decision on a character centered in its input window, as well as to estimate the distance of the current and next character from the center of the input window. The net learns to accurately estimate these distances regardless of variations in character width, spacing between characters, writing style and other factors.


Learning to See Where and What: Training a Net to Make Saccades and Recognize Handwritten Characters

Neural Information Processing Systems

This paper describes an approach to integrated segmentation and recognition of hand-printed characters. The approach, called Saccade, integrates ballistic and corrective saccades (eye movements) with character recognition. A single backpropagation net is trained to make a classification decision on a character centered in its input window, as well as to estimate the distance of the current and next character from the center of the input window. The net learns to accurately estimate these distances regardless of variations in character width, spacing between characters, writing style and other factors.


Penguins Can Make Cake

AI Magazine

Since this article is a counting argument, the conclusion time, a number of alternatives have been proposed. Presumably, in realistic cases, the Universally Bad Idea," analyzes one such number of sensors is large enough that a universal alternative, Marcel Schoppers's universal plan could not fit in your head. He also extends this analysis to a There are two reasons not to be concerned number of other systems, including Pengi about this apparent problem. They involve (A gre and Chapman 1987), which was structure and state, designed by Phil Agre and myself. Ginsberg's criticisms of universal plans rest Using universal plans, he says, is infeasible because their size is exponential in the number of possible domain states. Representing such a plan is infeasible in even quite small realistic domains. I'm sympathetic to such arguments, having made similar ones to the effect that classical planning is infeasible (Agre and Chapman 1988; Chapman 1987b). I don't understand the details of Schoppers's ideas, so I'm not sure whether this critique of universal plans per se is correct. However, I show that these arguments do not extend to Pengi. Ginsberg calls Pengi an approximate universal plan, by which he means it is like a universal plan except that it does not correctly specify what to do in every situation. However, Pengi's operation involves no plans, universal or approximate, and Pengi and universal plans, although they share some motivations, have little to do with each other as technical proposals. Ginsberg suggests number of its inputs. Pengi-like system, computation in the number of pixels or that, Blockhead, which efficiently solves the fruitcake on the average, business data processing takes problem; the way it solves it elucidates exponential work in the number of records. They have a lot The fruitcake problem is to stack a set of of structure to them, and this structure can be labeled blocks so that they spell the word exploited to exponentially reduce the computation's fruitcake. What is apparently difficult about size. I show impossible under the rules of the domain, Blockhead solving a problem involving 45 and the remainder can be categorized relatively blocks in which there are 45! 1056 configurations, cheaply to permit abstraction and There is every in every configuration, so it is not by reason to think that this same structure is approximation that it succeeds. Indeed, Ginsberg makes this and a central system. The [planning couldn't work if] there were no visual system is a small subset of Pengi's rhyme or reason to things."