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Dimitris Tsipras

15 accepted papers

2022

What Can Transformers Learn In-Context? A Case Study of Simple Function Classes

NeurIPS 2022accept

In-context learning is the ability of a model to condition on a prompt sequence consisting of in-context examples (input-output pairs corresponding to some task) along with a new query input, and generate the corresponding output. Crucially, in-context learning happens only at inference time without…

2021

Editing a classifier by rewriting its prediction rules

NeurIPS 2021poster

We propose a methodology for modifying the behavior of a classifier by directly rewriting its prediction rules. Our method requires virtually no additional data collection and can be applied to a variety of settings, including adapting a model to new environments, and modifying it to ignore spurious…

2020

A Closer Look at Deep Policy Gradients

ICLR 2020talk

We study how the behavior of deep policy gradient algorithms reflects the conceptual framework motivating their development. To this end, we propose a fine-grained analysis of state-of-the-art methods based on key elements of this framework: gradient estimation, value prediction, and optimization la…

Cited by 98SourceScholar
2020

From ImageNet to Image Classification: Contextualizing Progress on Benchmarks

ICML 2020poster

Building rich machine learning datasets in a scalable manner often necessitates a crowd-sourced data collection pipeline. In this work, we use human studies to investigate the consequences of employing such a pipeline, focusing on the popular ImageNet dataset. We study how specific design choices in…

2020

Identifying Statistical Bias in Dataset Replication

ICML 2020poster

Dataset replication is a useful tool for assessing whether improvements in test accuracy on a specific benchmark correspond to improvements in models’ ability to generalize reliably. In this work, we present unintuitive yet significant ways in which standard approaches to dataset replication introdu…

2020

Implementation Matters in Deep RL: A Case Study on PPO and TRPO

ICLR 2020talk

We study the roots of algorithmic progress in deep policy gradient algorithms through a case study on two popular algorithms: Proximal Policy Optimization (PPO) and Trust Region Policy Optimization (TRPO). Specifically, we investigate the consequences of "code-level optimizations:" algorithm augment…

Cited by 211SourceScholar
2019

Adversarial Examples Are Not Bugs, They Are Features

NeurIPS 2019spotlight

Adversarial examples have attracted significant attention in machine learning, but the reasons for their existence and pervasiveness remain unclear. We demonstrate that adversarial examples can be directly attributed to the presence of non-robust features: features (derived from patterns in the data…

2019

Exploring the Landscape of Spatial Robustness

ICML 2019oral

The study of adversarial robustness has so far largely focused on perturbations bound in $\ell_p$-norms. However, state-of-the-art models turn out to be also vulnerable to other, more natural classes of perturbations such as translations and rotations. In this work, we thoroughly investigate the vul…

2019

Image Synthesis with a Single (Robust) Classifier

NeurIPS 2019poster

We show that the basic classification framework alone can be used to tackle some of the most challenging tasks in image synthesis. In contrast to other state-of-the-art approaches, the toolkit we develop is rather minimal: it uses a single, off-the-shelf classifier for all these tasks. The crux of o…

Cited by 210SourcePDFScholar
2019

Robustness May Be at Odds with Accuracy

ICLR 2019poster

We show that there exists an inherent tension between the goal of adversarial robustness and that of standard generalization. Specifically, training robust models may not only be more resource-consuming, but also lead to a reduction of standard accuracy. We demonstrate that this trade-off between t…

Cited by 2099SourcePDFScholar
2018

Adversarially Robust Generalization Requires More Data

NeurIPS 2018spotlight

Machine learning models are often susceptible to adversarial perturbations of their inputs. Even small perturbations can cause state-of-the-art classifiers with high "standard" accuracy to produce an incorrect prediction with high confidence. To better understand this phenomenon, we study adversaria…

Cited by 962SourcePDFScholar
2018

How Does Batch Normalization Help Optimization?

NeurIPS 2018oral

Batch Normalization (BatchNorm) is a widely adopted technique that enables faster and more stable training of deep neural networks (DNNs). Despite its pervasiveness, the exact reasons for BatchNorm's effectiveness are still poorly understood. The popular belief is that this effectiveness stems from…

Cited by 2422SourcePDFScholar
2018

Towards Deep Learning Models Resistant to Adversarial Attacks

ICLR 2018poster

Recent work has demonstrated that neural networks are vulnerable to adversarial examples, i.e., inputs that are almost indistinguishable from natural data and yet classified incorrectly by the network. To address this problem, we study the adversarial robustness of neural networks through the lens o…

Cited by 15225SourcePDFScholar