README.md

# ROSA+
**ROSA+**: RWKV's ROSA implementation with fallback statistical predictor
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<img width="700" alt="image" src="https://github.com/user-attachments/assets/606a4d61-87b8-4bfc-ac27-564528042605" />
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## What is ROSA+?
**ROSA+** is an extension of the **statistical next-token predictor** [proposed by BlinkDL](https://x.com/BlinkDL_AI/status/1976912771985146184) in extending the RWKV language model. It provides an intuitive Python interface as well as a fallback Witten–Bell predictor for unknown sequences.

## Example Usage in Python
The implementation is self-contained in `rosaplus.py`. You can download the repository and use it from there.

```python
# example.py
from rosaplus import ROSAPlus
import requests

# Train on Shakespare
url = "https://raw.githubusercontent.com/karpathy/char-rnn/master/data/tinyshakespeare/input.txt"

# Download the text
response = requests.get(url)
text = response.text
print("Downloaded text.")

# Initialize model
m = ROSAPlus(max_order=1048576, use_eot=False, seed=0) 
m.train_example(text) # Train ROSA
m.build_lm() # Train fallback predictor

# Prompting
prompt = "ROMEO:" # Novel text
max_tokens = 256

# Eval mode
print(prompt + m.generate(prompt, steps=max_tokens))

# Saving model
m.save("rosa-model.json")
m2 = ROSAPlus.load("rosa-model.json") # Loading model
```

**Output:** (verbatim)
```
ROMEO:
In faith, I will. Let me peruse this face.
Mercutio's kinsman, noble County Paris!
What said my man, when my betossed soul
Did not attend him as we rode? I think
...
```

## Novel Text Generation
ROSA+ can also be used to generate novel sequences that **do not show up in the training dataset.** You can enable this by **always** using the fallback predictor. It often leads to coherent, surprising results.
```python
# add always_fallback=True to the example
print(prompt + m.generate(prompt, steps=max_tokens, always_fallback=True))
```

**Output:** (novel)
```
ROMEO:
The exchange of joy
That only Warwick's daughter.

CLARENCE:
To whom, my lord; the foe vantage.
But make you read no other, and look'd deadly that name remains;
The cruelty and envy of the people,
Permitted by our faces
For man or master; then it for some
```

As you can see, these arrangement of sentences do not show up in the dataset (CTRL+F). Rather, ROSA+ intelligently splices and pulls together the features from ROSA to perform next-character prediction.

For any given prefix, you can also get the probability distribution for the next token:
```python
# Eval mode
print(m.get_dist("ROMEO:\nOh, how could yo"))
```

Output:
```
{'u': 0.9999989177710094, 'n': 5.442332067424175e-07, 'k': 5.379892385443467e-07, 'r': 6.0439900862193395e-12, ' ...
```

As you can see, ROSA+ is extremely confident that 'u' is the next token (and it is correct!)

## RWKV Support
This is just a standalone example of ROSA and does not provide RWKV integration. You will have to go to the RWKV Discord or ask the main maintainer (BlinkDL) for assistance in this regard.

## Extensions
ROSA+ extends ROSA by:

- Allowing training and sampling on individual sequences, similar to a LLM
- Utilizing a (coherent) fallback Witten–Bell based predictor for when ROSA is unsure of the next token.

This makes it extremely fast, since ROSA is used for 99% of the predictions and the fallback only occurs for novel sequences.

**Tokenization:** The default tokenization is character-based (I will add support for new tokenizers coming soon.)

## Notes

If you install [orjson](https://github.com/ijl/orjson), it will use it automatically and lead to far faster import/export speed.
Docs coming soon.

## Issues with ROSA+

ROSA+ is entirely statistical-based -- it extends upon the ROSA predictor proposed by BlinkDL, then provides a probability predictor as a fallback. However, this means it only has a **database-like** understanding of text -- it can **stitch together multiple sentences** and **demonstrate grammar**, but it lacks the same context understanding as an NN (RWKV, Transformer etc.)

For instance, when trained on Shakespeare, and with `always_fallback=True` (forcing novel predictions), it generates text that "looks right", but switches between characters every stanza.

```
COMINIUS:
Well, one nail;
Right noble is thy mercy dried their watches of chance and thy lord's false love;
For both of you are birds of selfsame feather.

KING EDWARD IV:
Peace, wilful boy, or I will charm your tongue.

CLARENCE:
Unhappy fortune! by my troth, I looked upon his faith iron cook you, sir, he bid me knocks; ha! let me be unrolled and said 'The better for our purpose.'

KING RICHARD III:
So proud the name of Henry with your holy look'd on me,
And wouldst do not break your oaths; for of that sin
May deny her aiding have these nothing here.

AUTOLYCUS:
I hope so, sir; for I have about me manner doth accuse my husband, I
...
```

A ChatGPT analysis of ROSA+'s lines uncovers some insight:
```
Short answer: it’s Shakespeare-flavored, not Shakespearean. It reads like a collage of misquoted or remixed lines, with scrambled idioms, mixed plays (Juliet/Romeo with Buckingham and Gaunt), and meter/grammar that don’t line up with blank verse.

Quick notes:

* “Now, by Saint Peter’s Church…” and “I have forgot why I did call thee back” echo *Romeo and Juliet*, but they’re spliced into new contexts.
* “The world goes his bonnet to an oystery” mangles Pistol’s “The world’s mine oyster.”
* Shifts between **you/thee/thou/thy** are inconsistent (use *thou* as subject, *thee* as object, *thy/thine* as possessives).
* Many lines don’t scan as iambic pentameter (10 syllables, mostly unstressed–stressed).
```

A true NN-based model would outperform a standalone ROSA+ implementation because of the understanding of actual context. While ROSA+ has impressive surface-level understanding, it lacks deeper, low level meaning expressed by NNs.


### Interesting occurences
You can view all the samples in the `samples` directory -- interestingly, in `sample_default_output.txt`, the model falls into an attractor state, repeating itself every ~3k lines, halfway through. However, in `sample_novel_output.txt`, you can spot some very novel sentences:
```
LADY ANNE:
Well, well, peace be with you, sir, he bid me know the points o' the dead
May walk again: if such thing but what I am,
I would wish it gone,
```

The phrases `Well, well, peace be with you` and `I would wish it gone` never show up in the training data.

## Use cases
- Autocorrect / word prediction
- Translation (possibly)
- Features for a lower level model
- Generating surface-level text that fools detectors

## Improving ROSA+
One may be able to create a coherent language model simply by feeding ROSA+ embeddings into a GRU. Since ROSA+ captures the immediate surface-level features of text, a sufficient neural network may be able to operate on these embeddings and alter the distribution for more fine-grained understanding.

## Downsides of statistical LMs
Unless statistical LMs incorporate some kind of **statistical attention mechanism** (which is possible!) they will never be able to grasp a high-level understanding of text as do humans and LMs. A statistical LM is unable to **copy data / tokens from one place to another**, **operate on a continous state**, **blend together tokens across different spaces**, perform **few-shot learning** (needs neural mechanism!) or **transfer learning** (no state vectors!). Therefore, their purpose remains limited to grasping **surface-level** features of text, like syntax, or general structure.

Google pushed to make their translation software (which in the 2010s, was n-gram based) the best at the time, but even **LSTMs** (which were invented way before Transformers) managed to outperform them.

Do not let this discourage you though. It may be practical to incorporate some kind of **continous state vector / representation** within a statistical model, making it **drastically more efficient than LLMs** while preserving all the benefits of **NN-based models.** This is an active field of research at **Bellevue College ML** (BCML) -- and if pioneered, could result in language models thousands of times more efficient. Don't let an article discourage you.