no code implementations • EMNLP 2021 • Clara Meister, Afra Amini, Tim Vieira, Ryan Cotterell
Beam search is the default decoding strategy for many sequence generation tasks in NLP.
1 code implementation • EMNLP 2021 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
In this paper, we adapt two spanning tree sampling algorithms to faithfully sample dependency trees from a graph subject to the root constraint.
no code implementations • 4 Dec 2024 • Tim Vieira, Ben LeBrun, Mario Giulianelli, Juan Luis Gastaldi, Brian DuSell, John Terilla, Timothy J. O'Donnell, Ryan Cotterell
Modern language models are internally -- and mathematically -- distributions over token strings rather than \emph{character} strings, posing numerous challenges for programmers building user applications on top of them.
1 code implementation • 3 Oct 2024 • Mario Giulianelli, Luca Malagutti, Juan Luis Gastaldi, Brian DuSell, Tim Vieira, Ryan Cotterell
The paper argues that token-level language models should be (approximately) marginalized into character-level language models before they are used in psycholinguistic studies to compute the surprisal of a region of interest; then, the marginalized character-level language model can be used to compute the surprisal of an arbitrary character substring, which we term a focal area, that the experimenter may wish to use as a predictor.
no code implementations • 16 Jul 2024 • Juan Luis Gastaldi, John Terilla, Luca Malagutti, Brian DuSell, Tim Vieira, Ryan Cotterell
The present paper contributes to addressing this theoretical gap by proposing a unified formal framework for representing and analyzing tokenizer models.
no code implementations • 8 Jul 2024 • Afra Amini, Tim Vieira, Ryan Cotterell
To the extent this fine-tuning is successful and we end up with a good approximation, we have reduced the inference cost by a factor of N. Our experiments on a controlled generation task suggest that while variational BoN is not as effective as BoN in aligning language models, it is close to BoN performance as vBoN appears more often on the Pareto frontier of reward and KL divergence compared to models trained with KL-constrained RL objective.
1 code implementation • 16 Feb 2024 • Afra Amini, Tim Vieira, Ryan Cotterell
DPO, as originally formulated, relies on binary preference data and fine-tunes a language model to increase the likelihood of a preferred response over a dispreferred response.
no code implementations • 27 Nov 2023 • Andreas Opedal, Eleftheria Tsipidi, Tiago Pimentel, Ryan Cotterell, Tim Vieira
The left-corner transformation (Rosenkrantz and Lewis, 1970) is used to remove left recursion from context-free grammars, which is an important step towards making the grammar parsable top-down with simple techniques.
no code implementations • 23 Oct 2023 • Alexandra Butoi, Tim Vieira, Ryan Cotterell, David Chiang
From these, we also immediately obtain stringsum and allsum algorithms for TAG, LIG, PAA, and EPDA.
1 code implementation • 6 Jul 2023 • Andreas Opedal, Ran Zmigrod, Tim Vieira, Ryan Cotterell, Jason Eisner
This paper provides a reference description, in the form of a deduction system, of Earley's (1970) context-free parsing algorithm with various speed-ups.
1 code implementation • 29 Jun 2023 • Vilém Zouhar, Clara Meister, Juan Luis Gastaldi, Li Du, Tim Vieira, Mrinmaya Sachan, Ryan Cotterell
Via submodular functions, we prove that the iterative greedy version is a $\frac{1}{{\sigma(\boldsymbol{\mu}^\star)}}(1-e^{-{\sigma(\boldsymbol{\mu}^\star)}})$-approximation of an optimal merge sequence, where ${\sigma(\boldsymbol{\mu}^\star)}$ is the total backward curvature with respect to the optimal merge sequence $\boldsymbol{\mu}^\star$.
1 code implementation • 17 Jan 2023 • Anej Svete, Benjamin Dayan, Tim Vieira, Ryan Cotterell, Jason Eisner
The pathsum in ordinary acyclic WFSAs is efficiently computed by the backward algorithm in time $O(|E|)$, where $E$ is the set of transitions.
1 code implementation • 13 Oct 2022 • Alexandra Butoi, Brian DuSell, Tim Vieira, Ryan Cotterell, David Chiang
Weighted pushdown automata (WPDAs) are at the core of many natural language processing tasks, like syntax-based statistical machine translation and transition-based dependency parsing.
1 code implementation • 14 Sep 2022 • Clemente Pasti, Andreas Opedal, Tiago Pimentel, Tim Vieira, Jason Eisner, Ryan Cotterell
It shows, by a simple construction, that the intersection of a context-free language and a regular language is itself context-free.
1 code implementation • NAACL 2022 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
However, practitioners rely on Monte Carlo approximation to perform this test due to a lack of a suitable exact algorithm.
1 code implementation • 22 Sep 2021 • Clara Meister, Afra Amini, Tim Vieira, Ryan Cotterell
In this work, we propose a new method for turning beam search into a stochastic process: Conditional Poisson stochastic beam search.
no code implementations • Findings (EMNLP) 2021 • Tim Vieira, Ryan Cotterell, Jason Eisner
To this end, we describe a set of program transformations, a simple metric for assessing the efficiency of a transformed program, and a heuristic search procedure to improve this metric.
no code implementations • 14 Sep 2021 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
Colbourn (1996)'s sampling algorithm has a running time of $\mathcal{O}(N^3)$, which is often greater than the mean hitting time of a directed graph.
1 code implementation • ACL 2021 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
Furthermore, we present a novel extension of the algorithm for decoding the K-best dependency trees of a graph which are subject to a root constraint.
1 code implementation • ACL 2021 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
In the case of second-order derivatives, our scheme runs in the optimal $\mathcal{O}(A^2 N^4)$ time where $A$ is the alphabet size and $N$ is the number of states.
1 code implementation • 1 Jun 2021 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
Furthermore, we present a novel extension of the algorithm for decoding the $K$-best dependency trees of a graph which are subject to a root constraint.
1 code implementation • 20 Oct 2020 • Matthew Francis-Landau, Tim Vieira, Jason Eisner
We present a scheme for translating logic programs, which may use aggregation and arithmetic, into algebraic expressions that denote bag relations over ground terms of the Herbrand universe.
Programming Languages Symbolic Computation
1 code implementation • EMNLP 2020 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
The connection between dependency trees and spanning trees is exploited by the NLP community to train and to decode graph-based dependency parsers.
1 code implementation • EMNLP 2020 • Clara Meister, Tim Vieira, Ryan Cotterell
This implies that the MAP objective alone does not express the properties we desire in text, which merits the question: if beam search is the answer, what was the question?
no code implementations • 29 Aug 2020 • Ran Zmigrod, Tim Vieira, Ryan Cotterell
We propose unified algorithms for the important cases of first-order expectations and second-order expectations in edge-factored, non-projective spanning-tree models.
1 code implementation • 8 Jul 2020 • Clara Meister, Tim Vieira, Ryan Cotterell
Decoding for many NLP tasks requires an effective heuristic algorithm for approximating exact search since the problem of searching the full output space is often intractable, or impractical in many settings.
1 code implementation • LREC 2020 • Aaron Steven White, Elias Stengel-Eskin, Siddharth Vashishtha, Venkata Govindarajan, Dee Ann Reisinger, Tim Vieira, Keisuke Sakaguchi, Sheng Zhang, Francis Ferraro, Rachel Rudinger, Kyle Rawlins, Benjamin Van Durme
We present the Universal Decompositional Semantics (UDS) dataset (v1. 0), which is bundled with the Decomp toolkit (v0. 1).
no code implementations • TACL 2017 • Tim Vieira, Jason Eisner
Pruning hypotheses during dynamic programming is commonly used to speed up inference in settings such as parsing.
no code implementations • TACL 2015 • Subhro Roy, Tim Vieira, Dan Roth
In order to address these quantitative reasoning problems we first develop a computational approach which we show to successfully recognize and normalize textual expressions of quantities.