Loading `tokenizer.model` with Rust API

[EricLBuehler]

Hello all,

Thank you for your excellent work here. I am trying to load a tokenizer.model file in my Rust application. However, it seems that the Tokenizer::from_file function only support loading from a tokenizer.json file. This causes problems as using a small script to save the tokenizer.json is error-prone and hard to discover for users. Is there a way to load a tokenizer.model file?

[ArthurZucker]

You cannot load a tokenizer.model, you need to write a converter. This is because it does not come from the tokenizers library but from either tiktoken or sentencepiece and there is no secret recipe. We need to adapt to the content of the file, but this is not super straight forward.

https://github.com/huggingface/transformers/blob/main/src/transformers/convert_slow_tokenizer.py#L544 is the simplest way to understand the process!

[EricLBuehler]

Ok, I understand. Do you know of a way or a library to do this in Rust without reaching for the Python transformers converter?

[ArthurZucker]

A library no, but we should be able to come up with a small rust code to do this 😉

[EricLBuehler]

@ArthurZucker are there any specifications or example loaders which I can look at to implement this?

[chenwanqq]

I also have the same question, for llava reasons😉

[ArthurZucker]

Yes! Actually the best way to do this is to use the converters from transformers see here: https://github.com/huggingface/transformers/blob/2965b204593df9d5652313386ec280ffbfd1753b/src/transformers/convert_slow_tokenizer.py#L1340 .

In rust we would need to read and parse the .model file with a sentencepiece loader.

[EricLBuehler]

Ok. Could I use this crate?

One other question: I am implementing GGUF to HF tokenizers conversion in mistral.rs, and have had success with the unigram model. I am adding the gpt2 = bpe model, but I was wondering what components of the Tokenizer are required such as the normalizer, post processor, etc., and also what decoder to use?

This is what I currently do: https://github.com/EricLBuehler/mistral.rs/blob/d66e5aff1e7faf208469c5bef3c70d45ffda5401/mistralrs-core/src/pipeline/gguf_tokenizer.rs#L116-L142, I would appreciate it if you could take a quick look and see if there is anything obviously wrong!

[vody-am]

oh I also have an interest in reading sentence piece tokenizers as well, in order to invoke the SigLIP text transformer in Rust!

EDIT: using the library mentioned by Eric above, I was able to load up https://huggingface.co/google/siglip-so400m-patch14-384/blob/main/spiece.model and it seemingly tokenized my input!

[ArthurZucker]

• @vody-am the support for fast SIGLIP tokenizer is on it's way, and should actually be pretty straighforward. https://github.com/huggingface/transformers/pull/29969

@EricLBuehler we actually shipped this in transformers, but sure I can have a look. Most of the tokenizers that are supported in GGUF format should use Metaspace per-tokenizer and decoder, BPE or unigram model, and either not normalizer or a precompile charset map. All the requirement are in the [convers_slow](https://github.com/huggingface/transformers/blob/8685b3c5d2dd2550527773d2a02499495a759e31/src/transformers/convert_slow_tokenizer.py#L56) in transformers.

I'll think about potentially automatically convert sentencepiece.model to rust, but the big problem is that I don't want to have to support sentencepiece + tiktoken, so might just be example gists / snippets of how to do this!

[EricLBuehler]

Thank you, @ArthurZucker for the link! I was actually able to get the GPT2 conversion to work now!

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