part 1:

basics() # Assignment 1: tokenization, model architecture, training

Tokenization

What are the atoms that the model operates on?

Formally: a tokenizer converts between raw inputs (bytes) and sequences of integers (tokens)

Popular tokenizer:

Byte-Pair Encoding(BPE)

[Sennrich+ 2015]

Intuition: break input into frequently-occuring chunks

Efficiency lens

The dream: tokenizer-free model architectures, which operate directly on bytes

[Xue+ 2021]

[Yu+ 2023]

[Pagnoni+ 2024]

[Deiseroth+ 2024]

[Hwang+ 2025]

These are promising, but have not yet been scaled up to the frontier.