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Comment by espadrine | Hacker News Reader

Did you mean to paste a different image? That diagram shows a much older design than the transformer coined in the 2017 paper. It doesn’t include token embeddings, doesn’t show multi-head attention, the part that looks like the attention mechanism doesn’t do self-attention and misses the query/key/value weight matrices, and the part that looks like the fully-connected layer is not done in the way depicted and doesn’t hook into self-attention in that way. Position embeddings and the way the blocks are stacked are also absent.

The FT article at least describes most of those aspects more accurately, although I was disappointed to see they got the attention mask wrong.

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> misses the query/key/value weight

Did you click the right link? The words "query", "key", and "value" are in the image! For the rest, you'll want to read the paper: https://arxiv.org/abs/2102.11174

Embeddings were around long before transformers.

The image only depicts a single attention head, of course.

Ah, I didn’t notice the picture came from Jürgen Schmidhuber. I understand his arguments, and his accomplishments are significant, but his 90s designs were not transformers, and lacked substantial elements that make them so efficient to train. He does have a bit of a reputation claiming that many recent discoveries should be attributed to, or give credit to, his early designs, which, while not completely unfounded, is mostly stretching the truth. Schmidhuber’s 2021 paper is interesting, but describes a different design, which while interesting, is not how the GPT family (or Llama 2, etc.) were trained.

The transformer absolutely uses many things that have been initially suggested in many previous papers, but its specific implementation and combination is what makes it work well. Talking about the query/key/value system, if the fully-connected layer is supposed to be some combination of the key and value weight matrices, the dimensionality is off (the embedding typically has the same vector size as the value (well, the combined size of values for each attention head, but the image doesn’t have attention heads) so that each transformer block has the same input structure), the query weight matrix is missing, and while the dotted lines are not explained in the image, the way the weights are optimized doesn’t seem to match what is shown.

Can you expand on what they got wrong?

Token embeddings typically only attend to past token embeddings, not future ones.

The reason is to enable significant parallelism during training: a large chunk of text goes through the transformer in a single pass, and its weights are optimized to make its output look like its input shifted by one token (ie. the transformer converts each input token to a predicted next token). However, if the attention weights attended to future tokens, they would strongly use the next token they are given, to predict that next token. So all future tokens are masked out.

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