Transformers

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Mllama

Overview

The Llama 3.2-Vision collection of multimodal large language models (LLMs) is a collection of pretrained and instruction-tuned image reasoning generative models in 11B and 90B sizes (text + images in / text out). The Llama 3.2-Vision instruction-tuned models are optimized for visual recognition, image reasoning, captioning, and answering general questions about an image.

Model Architecture: Llama 3.2-Vision is built on top of Llama 3.1 text-only model, which is an auto-regressive language model that uses an optimized transformer architecture. The tuned versions use supervised fine-tuning (SFT) and reinforcement learning with human feedback (RLHF) to align with human preferences for helpfulness and safety. To support image recognition tasks, the Llama 3.2-Vision model uses a separately trained vision adapter that integrates with the pre-trained Llama 3.1 language model. The adapter consists of a series of cross-attention layers that feed image encoder representations into the core LLM.

Usage Tips

For image+text and text inputs use MllamaForConditionalGeneration.
For text-only inputs use MllamaForCausalLM for generation to avoid loading vision tower.
Each sample can contain multiple images, and the number of images can vary between samples. The processor will pad the inputs to the maximum number of images across samples and to a maximum number of tiles within each image.
The text passed to the processor should have the "<|image|>" tokens where the images should be inserted.
The processor has its own apply_chat_template method to convert chat messages to text that can then be passed as text to the processor.

Mllama has an extra token used as a placeholder for image positions in the text. It means that input ids and an input embedding layer will have an extra token. But since the weights for input and output embeddings are not tied, the lm_head layer has one less token and will fail if you want to calculate loss on image tokens or apply some logit processors. In case you are training, make sure to mask out special "<|image|>" tokens in the labels as the model should not be trained on predicting them.

Otherwise if you see CUDA-side index erros when generating, use the below code to expand the lm_head by one more token.

old_embeddings = model.get_output_embeddings()

num_tokens = model.vocab_size + 1
resized_embeddings = model._get_resized_lm_head(old_embeddings, new_num_tokens=num_tokens, mean_resizing=True)
resized_embeddings.requires_grad_(old_embeddings.weight.requires_grad)
model.set_output_embeddings(resized_embeddings)

Usage Example

Instruct model

import requests
import torch
from PIL import Image
from transformers import MllamaForConditionalGeneration, AutoProcessor

model_id = "meta-llama/Llama-3.2-11B-Vision-Instruct"
model = MllamaForConditionalGeneration.from_pretrained(model_id, device_map="auto", torch_dtype=torch.bfloat16)
processor = AutoProcessor.from_pretrained(model_id)

messages = [
    [
        {
            "role": "user", 
            "content": [
                {"type": "image"},
                {"type": "text", "text": "What does the image show?"}
            ]
        }
    ],
]
text = processor.apply_chat_template(messages, add_generation_prompt=True)

url = "https://llava-vl.github.io/static/images/view.jpg"
image = Image.open(requests.get(url, stream=True).raw)

inputs = processor(text=text, images=image, return_tensors="pt").to(model.device)
output = model.generate(**inputs, max_new_tokens=25)
print(processor.decode(output[0]))

Base model

import requests
import torch
from PIL import Image
from transformers import MllamaForConditionalGeneration, AutoProcessor

model_id = "meta-llama/Llama-3.2-11B-Vision"
model = MllamaForConditionalGeneration.from_pretrained(model_id, device_map="auto", torch_dtype=torch.bfloat16)
processor = AutoProcessor.from_pretrained(model_id)

prompt = "<|image|>If I had to write a haiku for this one"
url = "https://llava-vl.github.io/static/images/view.jpg"
raw_image = Image.open(requests.get(url, stream=True).raw)

inputs = processor(text=prompt, images=raw_image, return_tensors="pt").to(model.device)
output = model.generate(**inputs, do_sample=False, max_new_tokens=25)
print(processor.decode(output[0], skip_special_tokens=True))

Transformers

Mllama

Overview

Usage Tips

Usage Example

Instruct model

Base model

MllamaConfig

class transformers.MllamaConfig

MllamaProcessor

class transformers.MllamaProcessor

batch_decode

decode

post_process_image_text_to_text

MllamaImageProcessor

class transformers.MllamaImageProcessor

pad

preprocess

resize

MllamaForConditionalGeneration

class transformers.MllamaForConditionalGeneration

forward

MllamaForCausalLM

class transformers.MllamaForCausalLM

forward

MllamaTextModel

class transformers.MllamaTextModel

forward

MllamaForCausalLM

class transformers.MllamaForCausalLM

forward

MllamaVisionModel

class transformers.MllamaVisionModel

forward