5 research outputs found
Do Neural Nets Learn Statistical Laws behind Natural Language?
The performance of deep learning in natural language processing has been
spectacular, but the reasons for this success remain unclear because of the
inherent complexity of deep learning. This paper provides empirical evidence of
its effectiveness and of a limitation of neural networks for language
engineering. Precisely, we demonstrate that a neural language model based on
long short-term memory (LSTM) effectively reproduces Zipf's law and Heaps' law,
two representative statistical properties underlying natural language. We
discuss the quality of reproducibility and the emergence of Zipf's law and
Heaps' law as training progresses. We also point out that the neural language
model has a limitation in reproducing long-range correlation, another
statistical property of natural language. This understanding could provide a
direction for improving the architectures of neural networks.Comment: 21 pages, 11 figure
Investigation on N-gram Approximated RNNLMs for Recognition of Morphologically Rich Speech
Recognition of Hungarian conversational telephone speech is challenging due
to the informal style and morphological richness of the language. Recurrent
Neural Network Language Model (RNNLM) can provide remedy for the high
perplexity of the task; however, two-pass decoding introduces a considerable
processing delay. In order to eliminate this delay we investigate approaches
aiming at the complexity reduction of RNNLM, while preserving its accuracy. We
compare the performance of conventional back-off n-gram language models (BNLM),
BNLM approximation of RNNLMs (RNN-BNLM) and RNN n-grams in terms of perplexity
and word error rate (WER). Morphological richness is often addressed by using
statistically derived subwords - morphs - in the language models, hence our
investigations are extended to morph-based models, as well. We found that using
RNN-BNLMs 40% of the RNNLM perplexity reduction can be recovered, which is
roughly equal to the performance of a RNN 4-gram model. Combining morph-based
modeling and approximation of RNNLM, we were able to achieve 8% relative WER
reduction and preserve real-time operation of our conversational telephone
speech recognition system.Comment: 12 pages, 2 figures, accepted for publication at SLSP 201
Ügyfélszolgálati beszélgetések nyelvmodellezése rekurrens neurális hálózatokkal
A spontán, társalgási beszĂ©d leĂrása a mai napig komoly kihĂvás elĂ© állĂtja a gĂ©pi beszĂ©dfelismerĹ‘ rendszereket. A tĂ©mák sokszĂnűsĂ©ge Ă©s a kevĂ©s tanĂtĂładat kĂĽlönösen megnehezĂti a nyelvi modellek tanĂtását. CikkĂĽnkben telefonos ĂĽgyfĂ©lszolgálati beszĂ©lgetĂ©seket modellezĂĽk rekurrens LSTM neurális hálĂłzat segĂtsĂ©gĂ©vel, mellyel közel felĂ©re sikerĂĽlt csökkentenĂĽnk a perplexitást a hagyományos, count n-gram modellhez kĂ©pest. Azt találtuk, hogy a rekurrens LSTM akkor is felĂĽlmĂşlja a count modell pontosságát, ha memĂłriája hosszát alacsonyra korlátozzuk (LSTM n-gram). 10 vagy annál nagyobb fokszámĂş LSTM n-grammal pedig a korlátozás nĂ©lkĂĽli LSTM nyelvi modell teljesĂtmĂ©nye is megközelĂthetĹ‘. Ez alapján arra következtetĂĽnk, hogy a rekurrens neurális nyelvi modellek pontosságának titka a hatĂ©kony simĂtásban rejlik, nem a hosszĂş távĂş memĂłriában. Az Ăşj, neurális nyelvmodell segĂtsĂ©gĂ©vel nem csak a perplexitást sikerĂĽlt csökkentenĂĽnk, hanem a kapcsolĂłdĂł beszĂ©dfelismerĂ©si feladaton a szĂłhiba-arányt is relatĂv 4%-kal