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The Taub Faculty of Computer Science Events and Talks

CS Lecture: Theoretical and practical principles for designing, training, and deploying huge language models
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Yoav Levine (AI21 Labs)
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Wednesday, 04.01.2023, 10:30
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Taub 601
The field of natural language processing (NLP) has been advancing in giant strides over the past several years. The main drivers of this success are: (1) scaling the Transformer deep network architecture to unprecedented sizes and (2) “pretraining” the Transformer over massive amounts of unlabeled text. In this talk, I will describe efforts to provide principled guidance for the above main components and further thrusts in contemporary NLP, aimed to serve as timely constructive feedback for the strong empirical pull in this field. I will begin by describing our theoretical framework for analyzing Transformers, and present results on the depth to width tradeoffs in Transformers, identified bottlenecks within internal Transformer dimensions, and identified biases introduced during the Transformer self-supervised pretraining phase. This framework has guided the design and scale of several of the largest existing language models, including Chinchilla by Deepmind (70 billion learned parameters), Bloom by BigScience (176 billion learned parameters), and Jurassic-1 by AI21(178 billion learned parameters). Then, I will describe our works on leveraging linguistic biases such as word senses or frequent n-grams in order to increase efficiency of the self-supervised pretraining phase. Subsequently, I will describe novel principles for addressing a present-day problem stemming from the above success of scaling, namely, how to deploy a huge language model such that it specializes in many different use cases simultaneously (e.g., supporting many different customer needs simultaneously). Finally, I will comment on future challenges in this field, and will relatedly present a recent theoretical result on the importance of intermediate supervision when solving composite NLP tasks. This talk is based on works published in NeurIPS 2020, ACL 2020, ICLR 2021 (spotlight), ICML 2021, ICLR 2022 (spotlight), ICML 2022 (workshop), as well as on several recent preprints. Bio: Dr. Yoav Levine serves as co-Chief Scientist at AI21 Labs, an Israeli start up in the field of NLP. He earned his PhD at the Hebrew University, under the supervision of Prof. Amnon Shashua. His PhD studies were supported by the Israeli Academy of Sciences Adams fellowship, and for them he has received the Blavatnik PhD Prize awarded to the top 5 Israeli PhD theses in the field of computer science. Prior to his doctoral studies, he earned an M.Sc. in theoretical condensed matter physics from the Weizmann Institute of Science under the supervision of Prof. Yuval Oreg, and a double B.Sc. in physics and electrical engineering (both summa cum laude) from Tel Aviv University, supported by the Adi Lautman excellence program.