Yannic

Source video: Retentive Network: A Successor to Transformer for Large Language Models (Paper Explained)

Remove softmax outside the attention scores, then no all the results have to be hold and wait for softmax.

• RetNet is a kind of linear transforemr, like RWKV.

• Recurrent network each time train only 1 token because once the next work has been predicted, the backpropagation has to be done to optimize previous hidden states.

• Recurrent network cannot be trained parallelly because the non-linearity activation function

  G(c( G(b( G(ax+γ)+γ )+γ) +γ) )

• Hidden state is a shared buffer. The hidden state contains all the previous information, so the memory cost is consistent during training.

  $$ \begin{aligned} ax+\gamma = \gamma \\ by + \gamma = \gamma \\ cz + \gamma = \gamma \\ \end{aligned} $$

• Transformer can’t be recurrent because the existence of softmax, which requires all the attention scores (“hidden states”) not to be abandoned.

• RetNet achieved training parallism through matrix multiplication, like a Linear layer.

• Time-scaling mask replaces causal mask (blocking the subsequent words when doing attention in parallel)

• RetNet by chunks is a trade-off between recurrent and parallel.

秋刀鱼

Source video: 【论文速览】 RetNet: A Successor to Transformer for Large Language Models2307.08621

Equentions explaination and code walkthrough.

1. A global state is maintained like recurrent network.
2. With that, expand the equation of attention: Q K V
3. Apply singular decomposition
4. ….