Search Results for author: Christos Papadimitriou

Found 15 papers, 4 papers with code

Masked Generative Story Transformer with Character Guidance and Caption Augmentation

1 code implementation13 Mar 2024 Christos Papadimitriou, Giorgos Filandrianos, Maria Lymperaiou, Giorgos Stamou

Story Visualization (SV) is a challenging generative vision task, that requires both visual quality and consistency between different frames in generated image sequences.

Language Modelling Large Language Model +1

On Limitations of the Transformer Architecture

no code implementations13 Feb 2024 Binghui Peng, Srini Narayanan, Christos Papadimitriou

What are the root causes of hallucinations in large language models (LLMs)?

The complexity of non-stationary reinforcement learning

no code implementations13 Jul 2023 Christos Papadimitriou, Binghui Peng

The problem of continual learning in the domain of reinforcement learning, often called non-stationary reinforcement learning, has been identified as an important challenge to the application of reinforcement learning.

Continual Learning reinforcement-learning

Neuroscience needs Network Science

no code implementations10 May 2023 Dániel L Barabási, Ginestra Bianconi, Ed Bullmore, Mark Burgess, SueYeon Chung, Tina Eliassi-Rad, Dileep George, István A. Kovács, Hernán Makse, Christos Papadimitriou, Thomas E. Nichols, Olaf Sporns, Kim Stachenfeld, Zoltán Toroczkai, Emma K. Towlson, Anthony M Zador, Hongkui Zeng, Albert-László Barabási, Amy Bernard, György Buzsáki

We explore the challenges and opportunities in integrating multiple data streams for understanding the neural transitions from development to healthy function to disease, and discuss the potential for collaboration between network science and neuroscience communities.

Memory Bounds for Continual Learning

no code implementations22 Apr 2022 Xi Chen, Christos Papadimitriou, Binghui Peng

We make novel uses of communication complexity to establish that any continual learner, even an improper one, needs memory that grows linearly with $k$, strongly suggesting that the problem is intractable.

Continual Learning

Nash, Conley, and Computation: Impossibility and Incompleteness in Game Dynamics

no code implementations26 Mar 2022 Jason Milionis, Christos Papadimitriou, Georgios Piliouras, Kelly Spendlove

We also prove a stronger result for $\epsilon$-approximate Nash equilibria: there are games such that no game dynamics can converge (in an appropriate sense) to $\epsilon$-Nash equilibria, and in fact the set of such games has positive measure.

Implementing Permutations in the Brain and SVO Frequencies of Languages

no code implementations17 Jun 2021 Denis Turcu, Christos Papadimitriou

More generally, we also formulate and algorithmically solve the problems of implementing a permutation of the leaves of any binary tree, and of selecting the permutation that is easiest to implement on a given binary tree.

Sentence

Self-Attention Networks Can Process Bounded Hierarchical Languages

1 code implementation ACL 2021 Shunyu Yao, Binghui Peng, Christos Papadimitriou, Karthik Narasimhan

Despite their impressive performance in NLP, self-attention networks were recently proved to be limited for processing formal languages with hierarchical structure, such as $\mathsf{Dyck}_k$, the language consisting of well-nested parentheses of $k$ types.

Hard Attention

Online Stochastic Max-Weight Bipartite Matching: Beyond Prophet Inequalities

no code implementations20 Feb 2021 Christos Papadimitriou, Tristan Pollner, Amin Saberi, David Wajc

This is the best possible ratio for this problem, as it generalizes the original single-item prophet inequality problem.

Data Structures and Algorithms

Learning with Plasticity Rules: Generalization and Robustness

no code implementations1 Jan 2021 Rares C Cristian, Max Dabagia, Christos Papadimitriou, Santosh Vempala

Here we hypothesize that (a) Brains employ synaptic plasticity rules that serve as proxies for GD; (b) These rules themselves can be learned by GD on the rule parameters; and (c) This process may be a missing ingredient for the development of ANNs that generalize well and are robust to adversarial perturbations.

The Platform Design Problem

no code implementations13 Sep 2020 Christos Papadimitriou, Kiran Vodrahalli, Mihalis Yannakakis

The Designer may design a platform for each of these activities/states; if a platform is adopted by the Agent, the transition probabilities of the Markov chain are affected, and so is the objective of the Agent.

A New Age of Computing and the Brain

no code implementations27 Apr 2020 Polina Golland, Jack Gallant, Greg Hager, Hanspeter Pfister, Christos Papadimitriou, Stefan Schaal, Joshua T. Vogelstein

In December 2014, a two-day workshop supported by the Computing Community Consortium (CCC) and the National Science Foundation's Computer and Information Science and Engineering Directorate (NSF CISE) was convened in Washington, DC, with the goal of bringing together computer scientists and brain researchers to explore these new opportunities and connections, and develop a new, modern dialogue between the two research communities.

α-Rank: Multi-Agent Evaluation by Evolution

1 code implementation4 Mar 2019 Shayegan Omidshafiei, Christos Papadimitriou, Georgios Piliouras, Karl Tuyls, Mark Rowland, Jean-Baptiste Lespiau, Wojciech M. Czarnecki, Marc Lanctot, Julien Perolat, Remi Munos

We introduce {\alpha}-Rank, a principled evolutionary dynamics methodology, for the evaluation and ranking of agents in large-scale multi-agent interactions, grounded in a novel dynamical game-theoretic solution concept called Markov-Conley chains (MCCs).

Mathematical Proofs

Cycles in adversarial regularized learning

no code implementations8 Sep 2017 Panayotis Mertikopoulos, Christos Papadimitriou, Georgios Piliouras

Regularized learning is a fundamental technique in online optimization, machine learning and many other fields of computer science.

Strategic Classification

2 code implementations23 Jun 2015 Moritz Hardt, Nimrod Megiddo, Christos Papadimitriou, Mary Wootters

Jury designs a classifier, and Contestant receives an input to the classifier, which he may change at some cost.

BIG-bench Machine Learning Classification +1

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