Change/remove default maximum length in run_glue.py
Author: aditya-malte
Pull request: yes

I propose one of the following:
1) A vast majority of models have maximum sequence length as 512. 128 as a maximum length is very misleading because of this reason  and hence I suggest we revise it to 512.
2) Totally remove this variable and set maximum length only based on model’s maximum length. The tokenizers library used in this example  already has code to take the minimum of (max_seq_length, max_model_seq_length). Why not just remove this redundancy and directly set it based on the model’s largest acceptable sequence length

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Comments:
@sgugger Can you review this extremely simple PR

Hi there. The default is actually the same as the legacy script and I don't see any reason to change it. It provides the results given in the README which are consistent with the paper.

Also a default of 512 won't work with models that have a smaller max_length like distilbert.

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.

Oh. Yeah, I didn’t know distilbert had a smaller max_len. I’d seen max_len at least greater than or equal to 512 until now.