Test/Predict on summarization task
Author: zyxnlp
Pull request: no

## Environment info
<!-- You can run the command `transformers-cli env` and copy-and-paste its output below.
     Don't forget to fill out the missing fields in that output! -->

- `transformers` version: 4.4.0.dev0
- Platform: Linux-5.3.0-53-generic-x86_64-with-glibc2.10
- Python version: 3.8.3
- PyTorch version (GPU?): 1.7.1 (True)
- Tensorflow version (GPU?): not installed (NA)
- Using GPU in script?: <fill in>
- Using distributed or parallel set-up in script?: <fill in>

### Who can help
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@patrickvonplaten, @patil-suraj
Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @jplu

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

HF projects:

- nlp datasets: [different repo](https://github.com/huggingface/nlp)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
- research_projects/distillation: @VictorSanh

 -->
- maintained examples using bart: @patrickvonplaten, @patil-suraj

## Information

Model I am using (Bart):

The problem arises when using:
* [ ] only have train and eval example, do not have test/predict example script
* [ ] my own modified scripts: (give details below)
* [ ] CUDA_VISIBLE_DEVICES=2,3 python examples/seq2seq/run_seq2seq.py \
    --model_name_or_path /home/yxzhou/experiment/ASBG/output/xsum_bart_large/ \
    --do_predict \
    --task summarization \
    --dataset_name xsum \
    --output_dir /home/yxzhou/experiment/ASBG/output/xsum_bart_large/test/ \
    --num_beams 1 \

The tasks I am working on is:
* [ ] CNNDAILYMAIL , XSUM



## Expected behavior

<!-- A clear and concise description of what you would expect to happen. -->

Use the above script to test on CNNDAILYMAIL and XSUM dataset, the program seems will be always stuck at training_step (e.g., 26/709)

Could you please kindly provide a test/predict example script of the summarization task (e.g., XSUM). Thank you so much!

Comments:
Hi,

could you please ask questions related to training of models on the [forum](https://discuss.huggingface.co/)?

All questions related to fine-tuning a model for summarization on CNN can be found [here](https://discuss.huggingface.co/search?q=summarization%20cnn) for example. 



> Hi,
> 
> could you please ask questions related to training of models on the [forum](https://discuss.huggingface.co/)?
> 
> All questions related to fine-tuning a model for summarization on CNN can be found [here](https://discuss.huggingface.co/search?q=summarization%20cnn) for example.

@NielsRogge Oh, thank you for your reminder, that really helped!

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