301 research outputs found
Internal Pattern Matching Queries in a Text and Applications
We consider several types of internal queries: questions about subwords of a
text. As the main tool we develop an optimal data structure for the problem
called here internal pattern matching. This data structure provides
constant-time answers to queries about occurrences of one subword in
another subword of a given text, assuming that ,
which allows for a constant-space representation of all occurrences. This
problem can be viewed as a natural extension of the well-studied pattern
matching problem. The data structure has linear size and admits a linear-time
construction algorithm.
Using the solution to the internal pattern matching problem, we obtain very
efficient data structures answering queries about: primitivity of subwords,
periods of subwords, general substring compression, and cyclic equivalence of
two subwords. All these results improve upon the best previously known
counterparts. The linear construction time of our data structure also allows to
improve the algorithm for finding -subrepetitions in a text (a more
general version of maximal repetitions, also called runs). For any fixed
we obtain the first linear-time algorithm, which matches the linear
time complexity of the algorithm computing runs. Our data structure has already
been used as a part of the efficient solutions for subword suffix rank &
selection, as well as substring compression using Burrows-Wheeler transform
composed with run-length encoding.Comment: 31 pages, 9 figures; accepted to SODA 201
2kenize: Tying Subword Sequences for Chinese Script Conversion
Simplified Chinese to Traditional Chinese character conversion is a common
preprocessing step in Chinese NLP. Despite this, current approaches have poor
performance because they do not take into account that a simplified Chinese
character can correspond to multiple traditional characters. Here, we propose a
model that can disambiguate between mappings and convert between the two
scripts. The model is based on subword segmentation, two language models, as
well as a method for mapping between subword sequences. We further construct
benchmark datasets for topic classification and script conversion. Our proposed
method outperforms previous Chinese Character conversion approaches by 6 points
in accuracy. These results are further confirmed in a downstream application,
where 2kenize is used to convert pretraining dataset for topic classification.
An error analysis reveals that our method's particular strengths are in dealing
with code-mixing and named entities.Comment: Accepted to ACL 202
An Overview on Language Models: Recent Developments and Outlook
Language modeling studies the probability distributions over strings of
texts. It is one of the most fundamental tasks in natural language processing
(NLP). It has been widely used in text generation, speech recognition, machine
translation, etc. Conventional language models (CLMs) aim to predict the
probability of linguistic sequences in a causal manner. In contrast,
pre-trained language models (PLMs) cover broader concepts and can be used in
both causal sequential modeling and fine-tuning for downstream applications.
PLMs have their own training paradigms (usually self-supervised) and serve as
foundation models in modern NLP systems. This overview paper provides an
introduction to both CLMs and PLMs from five aspects, i.e., linguistic units,
structures, training methods, evaluation methods, and applications.
Furthermore, we discuss the relationship between CLMs and PLMs and shed light
on the future directions of language modeling in the pre-trained era
Online Embedding Compression for Text Classification using Low Rank Matrix Factorization
Deep learning models have become state of the art for natural language
processing (NLP) tasks, however deploying these models in production system
poses significant memory constraints. Existing compression methods are either
lossy or introduce significant latency. We propose a compression method that
leverages low rank matrix factorization during training,to compress the word
embedding layer which represents the size bottleneck for most NLP models. Our
models are trained, compressed and then further re-trained on the downstream
task to recover accuracy while maintaining the reduced size. Empirically, we
show that the proposed method can achieve 90% compression with minimal impact
in accuracy for sentence classification tasks, and outperforms alternative
methods like fixed-point quantization or offline word embedding compression. We
also analyze the inference time and storage space for our method through FLOP
calculations, showing that we can compress DNN models by a configurable ratio
and regain accuracy loss without introducing additional latency compared to
fixed point quantization. Finally, we introduce a novel learning rate schedule,
the Cyclically Annealed Learning Rate (CALR), which we empirically demonstrate
to outperform other popular adaptive learning rate algorithms on a sentence
classification benchmark.Comment: Accepted in Thirty-Third AAAI Conference on Artificial Intelligence
(AAAI 2019
Spoken content retrieval: A survey of techniques and technologies
Speech media, that is, digital audio and video containing spoken content, has blossomed in recent years. Large collections are accruing on the Internet as well as in private and enterprise settings. This growth has motivated extensive research on techniques and technologies that facilitate reliable indexing and retrieval. Spoken content retrieval (SCR) requires the combination of audio and speech processing technologies with methods from information retrieval (IR). SCR research initially investigated planned speech structured in document-like units, but has subsequently shifted focus to more informal spoken content produced spontaneously, outside of the studio and in conversational settings. This survey provides an overview of the field of SCR encompassing component technologies, the relationship of SCR to text IR and automatic speech recognition and user interaction issues. It is aimed at researchers with backgrounds in speech technology or IR who are seeking deeper insight on how these fields are integrated to support research and development, thus addressing the core challenges of SCR
Neural Machine Translation of Rare Words with Subword Units
Neural machine translation (NMT) models typically operate with a fixed
vocabulary, but translation is an open-vocabulary problem. Previous work
addresses the translation of out-of-vocabulary words by backing off to a
dictionary. In this paper, we introduce a simpler and more effective approach,
making the NMT model capable of open-vocabulary translation by encoding rare
and unknown words as sequences of subword units. This is based on the intuition
that various word classes are translatable via smaller units than words, for
instance names (via character copying or transliteration), compounds (via
compositional translation), and cognates and loanwords (via phonological and
morphological transformations). We discuss the suitability of different word
segmentation techniques, including simple character n-gram models and a
segmentation based on the byte pair encoding compression algorithm, and
empirically show that subword models improve over a back-off dictionary
baseline for the WMT 15 translation tasks English-German and English-Russian by
1.1 and 1.3 BLEU, respectively.Comment: accepted at ACL 2016; new in this version: figure
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