# Summarization (Seq2Seq model) training examples

The following example showcases how to finetune a sequence-to-sequence model for summarization
using the JAX/Flax backend.

JAX/Flax allows you to trace pure functions and compile them into efficient, fused accelerator code on both GPU and TPU.
Models written in JAX/Flax are **immutable** and updated in a purely functional
way which enables simple and efficient model parallelism.

`run_summarization_flax.py` is a lightweight example of how to download and preprocess a dataset from the 🤗 Datasets library or use your own files (jsonlines or csv), then fine-tune one of the architectures above on it.

For custom datasets in `jsonlines` format please see: https://huggingface.co/docs/datasets/loading_datasets.html#json-files and you also will find examples of these below.

Let's start by creating a model repository to save the trained model and logs.
Here we call the model `"bart-base-xsum"`, but you can change the model name as you like.

You can do this either directly on [huggingface.co](https://huggingface.co/new) (assuming that
you are logged in) or via the command line:

```
huggingface-cli repo create bart-base-xsum
```
Next we clone the model repository to add the tokenizer and model files.
```
git clone https://huggingface.co/<your-username>/bart-base-xsum
```
To ensure that all tensorboard traces will be uploaded correctly, we need to 
track them. You can run the following command inside your model repo to do so.

```
cd bart-base-xsum
git lfs track "*tfevents*"
```

Great, we have set up our model repository. During training, we will automatically
push the training logs and model weights to the repo.

Next, let's add a symbolic link to the `run_summarization_flax.py`.

```bash
export MODEL_DIR="./bart-base-xsum"
ln -s ~/transformers/examples/flax/summarization/run_summarization_flax.py run_summarization_flax.py
```

### Train the model
Next we can run the example script to train the model:

```bash
python run_summarization_flax.py \
	--output_dir ${MODEL_DIR} \
	--model_name_or_path facebook/bart-base \
	--tokenizer_name facebook/bart-base \
	--dataset_name="xsum" \
	--do_train --do_eval --do_predict --predict_with_generate \
	--num_train_epochs 6 \
	--learning_rate 5e-5 --warmup_steps 0 \
	--per_device_train_batch_size 64 \
	--per_device_eval_batch_size 64 \
	--overwrite_output_dir \
	--max_source_length 512 --max_target_length 64 \
	--push_to_hub
```

This should finish in 37min, with validation loss and ROUGE2 score of 1.7785 and 17.01 respectively after 6 epochs. training statistics can be accessed on [tfhub.de](https://tensorboard.dev/experiment/OcPfOIgXRMSJqYB4RdK2tA/#scalars).

> Note that here we used default `generate` arguments, using arguments specific for `xsum` dataset should give better ROUGE scores.