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Decoder-only transformer

As explained in Sutskever's List

A transformer language-model architecture that generates sequences using only a decoder stack, without a separate encoder.

A decoder-only transformer generates text from left to right, conditioning each token on those before it through masked self-attention. Introduced in 2018, it handles long input sequences better than the original Transformer and scales more easily than encoder-decoder counterparts. section 6.1.1

Scaling experiments compared decoder-only transformers with other architectures and found advantages in maintaining performance across long contexts and computational efficiency at scale. The results also showed that scaling curves were not unique to one architecture. section 6.1.1 section 6.1.5

Directional knowledge

GPT-4 can identify Tom Cruise’s mother when asked about him, yet fail to retrieve Tom Cruise when prompted with her name. This illustrates how left-to-right prediction can make reversing a relation brittle. section 7.5.2

Figure 7.7 BERT is deeply bidirectional, OpenAI’s GPT is unidirectional, and ELMo is shallowly bidirectional.
figure

Compare the directional context available to GPT with the bidirectional representations of BERT. section 7.5.2

How Sutskever's List covers it

How deep it goes
Explains left-to-right conditioning through masked self-attention and compares long-context performance and computational efficiency.
Examples
Contrasts LSTMs' short-sequence performance with their plateau and uses GPT-4's Tom Cruise example to illustrate directional brittleness.
What you can do after
Evaluate architecture trade-offs in long-context performance and computational efficiency at scale.
How it connects
Connects decoder-only transformers to autoregressive prediction, masked self-attention, GPT, BERT, LSTMs, and the Universal Transformer.

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This explainer was generated by Manning's knowledge graph from the text of Sutskever's List. The section links point to the parts of the book it draws on.