I wasn't aware that GPT-3 and GPT-4 use different tokenizers. I've read https://github.com/openai/openai-cookbook/blob/main/examples... and misinterpreted "ChatGPT models like gpt-3.5-turbo and gpt-4 use tokens in the same way as older completions models, ..." as GPT-3 and GPT-4 using the same tokenizer except for im_ tokens. Now I can see so many improvements, including the encoding of whitespaces and digits.