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Mitigating Open-Vocabulary Caption Hallucinations

<a href="https://assafbk.github.io/website/">Assaf Ben-Kish</a>, <a href="https://scholar.google.com/citations?user=ZsXf6OMAAAAJ&hl=en">Moran Yanuka</a>, <a href="https://morrisalp.github.io/">Morris Alper</a>, <a href="https://www.giryes.sites.tau.ac.il/">Raja Giryes</a>, <a href="https://www.elor.sites.tau.ac.il/">Hadar Averbuch-Elor</a>

Hallucinated details are prevalent in the outputs of modern image captioning models. Prior work has largely focused on detecting or mitigating hallucinations by using closed-vocabulary object lists, which simplify the problem but fail to capture most types of hallucinations that occur in practice. By leveraging recent progress in generative foundation models, we propose a unified framework for quantifying and mitigating open-vocabulary hallucinations.

First, We introduce OpenCHAIR, a benchmark for evaluating open-vocabulary hallucinations which surpasses the existing benchmark CHAIR both in diversity and accuracy:

Additionally, we introduce MOCHa, a reinforcement learning-based approach that adjusts captioning models to output detailed, valid captions while avoiding such hallucinations:

Setup

Clone Project

git clone https://github.com/assafbk/mocha_code.git
cd mocha_code

Create Environment

To set up our environment, please run:

conda env create -f environment.yml
conda activate mocha
python -m spacy download en_core_web_sm

Measure Open-Vocabulary Hallucination Rate With The OpenCHAIR Benchmark

To perform evaluation over the OpenCHAIR benchmark:

Create a csv file with a single column titled 'generated_caption'. The following rows should contain the model's captions for OpenCHAIR's images. An example csv file can be found in: OpenCHAIR/example_gen_file.csv

Additionally, we provide a script for generating such a file for the MOCHa-optimized BLIP-Base model, by running:
```
python OpenCHAIR/generate_captions.py \
 --model-ckpt moranyanuka/blip-image-captioning-base-mocha \
 --prompt "a photography of " \
 --batch-size 100
 --num-beams 5
```
Additional information:
- model-ckpt: The huggingface ckeckpoint of the model to be evaluated. Note that the script currently only supports BLIP-Base and BLIP-Large based models.
- prompt: The prompt appended for the generation
Download the Concreteness Rating Dataset (xlsx format) from here.

Run the evaluation script:

python OpenCHAIR/evaluate.py \
    --concreteness-dataset-path <path-to-concreteness-dataset> \
    --generations-file-path <path-to-generated-captions-file>

More configuration options can be found in OpenCHAIR/evaluate.py

The OpenCHAIR dataset can also be accessed from 🤗 Here, and can be loaded as follows:

from datasets import load_dataset
dataset = load_dataset("moranyanuka/OpenCHAIR")['test']

Tips:

selecting a large --batch-size can significantly improve the evaluation script's runtime.

Fine-Tune A Vision-Language Model With The MOCHa Framework

We currently support BLIP-Large on the MS-COCO Dataset (will add support for other models and datasets in the near future).

To run the training script:

python vlm_rlhf.py

The configuration file is vlm_rlhf_config.json. Important configurations:

reward_model_weights: List of weights for all rewards. First is the NLI weight and the second is the BERTScore weight (equivalent to alpha and 1-alpha in the paper). This field tunes the pareto frontier of the fidelity-adequacy curve. Initialized to [0.5,0.5].
beta: The weight for the kl-penalty reward. Initialized to 0.06.
num_of_images_per_batch: Number of images per PPO batch. Initialized to 10.
num_of_samples_per_image: Number of captions to generate per image. Initialized to 10. In a single batch there are <num_of_images_per_batch> x <num_of_samples_per_image> captions.
model_device, ref_model_device, reward_model_device: Cuda device for each model.

All training metrics, including caption samples (for train and verification images) are displayed in the wandb webpage.

Additional configurations:

output_dir: Where to save model checkpoints. Initialized to <project_dir>/output.
cache_dir: Huggingface cache dir for all models. Initialized to <project_dir>/hf_cache.
activate_logging: Enables wandb logging. Initialized to True.
sampling_temperature: Sampling temperature for the model. Initialized to 1.2.
save_steps: Model saving interval. Initialized to 200 (Note: best model is always saved regardless of this value).
eval_steps: Model evaluation interval. Initialized to 10.
max_step: Maximal amount of training steps. Initialized to 3000.

Check out vlm_rlhf_config.json for more configurations.

Final Model Weights

Model type	Checkpoint
Blip-Base	🤗 moranyanuka/blip-image-captioning-base-mocha
Blip-Large	🤗 moranyanuka/blip-image-captioning-large-mocha

We will publish the checkpoints of additional models in the near future.

Tips:

If more than one GPU is available, we recommend setting model_device to the first GPU, and ref_model_device and reward_model_device to the second GPU. (Motivation - the former requires grads hence uses the GPU memory more extensively).
If CUDA is running out of memory, try reducing the batch size (num_of_images_per_batch or num_of_samples_per_image or both).
To track the learning progress, keep an eye on the generated captions of the verification images (wandb -> Tables -> runs.summary["validation_data"])
Additionally, it is helpful to look after validation_reward_mean and kl_dist (wandb -> Charts). The kl_dist should not be too large (in BLIP-Large, empirically, no more than 5). In parallel, we want to see validation_reward_mean increase under the small kl_dist constraint. kl_dist is controlled by beta (decreases when we increase beta).

Citation

If you find this useful for your research, please cite the following:

@misc{benkish2024mitigating,
      title={Mitigating Open-Vocabulary Caption Hallucinations}, 
      author={Assaf Ben-Kish and Moran Yanuka and Morris Alper and Raja Giryes and Hadar Averbuch-Elor},
      year={2024},
      eprint={2312.03631},
      archivePrefix={arXiv},
      primaryClass={cs.CV}
}