Model Hub hanging in model's loading
@Narsil when loading some models, the loading hangs at 80-90%.

<img width="768" alt="Schermata 2021-01-11 alle 16 17 31" src="https://user-images.githubusercontent.com/163333/104202185-e0b12f00-542a-11eb-9e34-27f88ca232ab.png">

In this case it's [this](https://huggingface.co/mrm8488/umberto-wikipedia-uncased-v1-finetuned-squadv1-it?text=Dove+vivo%3F) one.
Adding some more info:

The api call returns to the model endpoint `503 (Service Unavailable)` and the error message
```json
 {"error":"Model Musixmatch/umberto-wikipedia-uncased-v1 is currently loading","estimated_time":10}
```

Then while the model is loading a new error comes out:

```
bundle.5e4ae99.js:1 Uncaught (in promise) TypeError: Failed to fetch
```

Thank you!<|||||>pinging @Narsil ! :)<|||||>Hi @loretoparisi ,

Sorry for the delayed answer. The problem was linked to you tokenizer that somehow had a failure when it was transformed automatically into a Fast one. (Actually it worked well, but the result could not be saved properly). I fixed your tokenizer by adding the precomputed result for Fast tokenizer:

https://huggingface.co/Musixmatch/umberto-wikipedia-uncased-v1/commit/483eca5f6b781ddb811e590fb584cc2e1d2b662e

Everything seems to be working properly now (and loads fast)
<|||||>@Narsil the inference outputs seem weird though, like the tokenizer doesn't uncase inputs: https://huggingface.co/Musixmatch/umberto-wikipedia-uncased-v1?text=Roma+%C3%A8+la+%3Cmask%3E+d%27Italia

<img width="709" alt="Screenshot 2021-01-22 at 19 47 53" src="https://user-images.githubusercontent.com/326577/105532172-79ac3980-5cb8-11eb-908d-9d9c7b3b80d9.png">
<|||||>- <unk> are explainable because this model uses only lowercase, so all MAJs are unks.
- c/a at start end was an error in the config (it might be because, there are some automatic fixed offsets for Camembert that might not actually be used by this model).
- The fact that some output are different from others is simply hardcoded in the widget (and is not correct IMHO)<|||||>@Narsil thank you for your help, there is anything that we can do/test by our side? cc @simonefrancia 
Thanks!<|||||>> * `<unk>` are explainable because this model uses only lowercase, so all MAJs are unks.

Sure, this means that there's some missing config for the tokenizer. See this model for example: https://huggingface.co/bert-base-uncased?text=Paris+is+the+%5BMASK%5D+of+France.



> * The fact that some output are different from others is simply hardcoded in the widget (and is not correct IMHO)

not sure what you mean here. cc @n1t0 <|||||>> Sure, this means that there's some missing config for the tokenizer. See this model for example: https://huggingface.co/bert-base-uncased?text=Paris+is+the+%5BMASK%5D+of+France.

I can't make any choice about what's more reasonable for the end model, the current tokenizer is exactly what `sentencepiece` would do (we export all variables from it, by using the `precompiled_charsmap`).
@loretoparisi if you want to actually force lowercasing input you can by changing `normalizer` within `tokenizer.json` to `Sequence` with a `Lowercase` then the `precompiled_charsmap`. But be aware that you won't have the same results as the raw SPM tokenizer anymore. Let me know if you want to do that I can do it, but again be careful of the impacts it could have for the model.

> not sure what you mean here. cc @n1t0

This: https://github.com/huggingface/moon-landing/blob/master/front/js-src/lib/widgets/text-classification.ts#L45
Also see PR on transformers that could solve this : https://github.com/huggingface/transformers/pull/9783<|||||>@Narsil I think there are several different things going on here:
 - The input doesn't get lowercased. This is true for both the fast and slow tokenizers, so yes, the conversion from slow to fast went well, but there's still a question about whether this should be fixed somehow (since the config contains `do_lowercase=True`, I think it was expected). If yes, both slow and fast tokenizers should be fixed.
 - Even if we don't look at the `<unk>`, the output still seems weird. After digging a bit, it seems that the IDs generated by the fast version of the tokenizer are not aligned with the slow one:
```python
from transformers import AutoTokenizer, pipeline


def run_input(input):
    tok_slow = AutoTokenizer.from_pretrained("Musixmatch/umberto-wikipedia-uncased-v1", use_fast=False)
    p_slow = pipeline("fill-mask", model="Musixmatch/umberto-wikipedia-uncased-v1", tokenizer=tok_slow)
    ids_slow = tok_slow.encode(input)
    p_output_slow = p_slow(input)

    tok_fast = AutoTokenizer.from_pretrained("Musixmatch/umberto-wikipedia-uncased-v1", use_fast=True)
    p_fast = pipeline("fill-mask", model="Musixmatch/umberto-wikipedia-uncased-v1", tokenizer=tok_fast)
    ids_fast = tok_fast.encode(input)
    p_output_fast = p_fast(input)

    print("Running with input: ", input)
    print("SLOW:")
    print(ids_slow)
    print(p_output_slow)

    print("FAST:")
    print(ids_fast)
    print(p_output_fast)


run_input("Roma è la <mask> d'Italia")
run_input("roma è la <mask> d'italia")
```
Gives the following output:
```python
Running with input:  Roma è la <mask> d'Italia
SLOW:
[5, 31908, 3, 31912, 79, 97, 51, 32004, 7, 31931, 3, 11007, 6]
[
{'sequence': "<s> <unk>oma è la lingua d'<unk>talia</s>", 'score': 0.04120568186044693, 'token': 1476, 'token_str': '▁lingua'}, 
{'sequence': "<s> <unk>oma è la città d'<unk>talia</s>", 'score': 0.023448798805475235, 'token': 521, 'token_str': '▁città'}, 
{'sequence': "<s> <unk>oma è la dea d'<unk>talia</s>", 'score': 0.022841867059469223, 'token': 4591, 'token_str': '▁dea'}, 
{'sequence': "<s> <unk>oma è la terra d'<unk>talia</s>", 'score': 0.02243848517537117, 'token': 1415, 'token_str': '▁terra'}, 
{'sequence': "<s> <unk>oma è la capitale d'<unk>talia</s>", 'score': 0.01755419932305813, 'token': 3152, 'token_str': '▁capitale'}
]
FAST:
[1, 31904, 0, 31908, 75, 93, 47, 32001, 3, 31927, 0, 11003, 2]
[
{'sequence': "<s> <unk>oma è laà d'<unk>talia</s>", 'score': 0.4644460380077362, 'token': 31936, 'token_str': 'à'},
{'sequence': "<s> <unk>oma è la<mask> d'<unk>talia</s>", 'score': 0.41339975595474243, 'token': 32001, 'token_str': '<mask>'},
{'sequence': "<s> <unk>oma è laena d'<unk>talia</s>", 'score': 0.02151116542518139, 'token': 408, 'token_str': 'ena'},
{'sequence': "<s> <unk>oma è laè d'<unk>talia</s>", 'score': 0.01422190386801958, 'token': 31935, 'token_str': 'è'},
{'sequence': "<s> <unk>oma è la ten d'<unk>talia</s>", 'score': 0.0057907504960894585, 'token': 685, 'token_str': '▁ten'}
]

Running with input:  roma è la <mask> d'italia
SLOW:
[5, 764, 97, 51, 32004, 7, 31931, 31911, 11007, 6]
[
{'sequence': "<s> roma è la bandiera d'italia</s>", 'score': 0.13166911900043488, 'token': 3525, 'token_str': '▁bandiera'},
{'sequence': "<s> roma è la capitale d'italia</s>", 'score': 0.0553407184779644, 'token': 3152, 'token_str': '▁capitale'},
{'sequence': "<s> roma è la nazionale d'italia</s>", 'score': 0.04516282677650452, 'token': 918, 'token_str': '▁nazionale'},
{'sequence': "<s> roma è la zona d'italia</s>", 'score': 0.022440679371356964, 'token': 1740, 'token_str': '▁zona'},
{'sequence': "<s> roma è la regione d'italia</s>", 'score': 0.02204475924372673, 'token': 1472, 'token_str': '▁regione'}
]
FAST:
[1, 760, 93, 47, 32001, 3, 31927, 31907, 11003, 2]
[
{'sequence': "<s> roma è la<mask> d'italia</s>", 'score': 0.9972749352455139, 'token': 32001, 'token_str': '<mask>'},
{'sequence': "<s> roma è laà d'italia</s>", 'score': 0.001777052297256887, 'token': 31936, 'token_str': 'à'},
{'sequence': "<s> roma è la pai d'italia</s>", 'score': 0.00022994846221990883, 'token': 14871, 'token_str': '▁pai'},
{'sequence': "<s> roma è la raffigura d'italia</s>", 'score': 0.00011272338451817632, 'token': 15184, 'token_str': '▁raffigura'},
{'sequence': "<s> roma è la hiv d'italia</s>", 'score': 0.00011238666047574952, 'token': 28952, 'token_str': '▁hiv'}
]
```
As you can see, the output using the slow tokenizer seems fine, while the other doesn't.<|||||>Okay this is now fixed: https://huggingface.co/Musixmatch/umberto-wikipedia-uncased-v1/commit/713d59922ccb4b5fc31a527ce2d785c23533363b

This 4 offset in the tokens is hardcoded for Camembert based tokenizers :
https://github.com/huggingface/transformers/blob/937f67074d6728f145d54d6ea87221a46303363d/src/transformers/models/camembert/tokenization_camembert.py#L241

I'm doing a pass on all BPE based spm to check various behaviors.<|||||>Hi @Narsil,
thanks for your support in Umberto.
thanks also for making Umberto wikipedia alive again.

We see something not usual that replaces <mask> token.
![Schermata 2021-02-10 alle 11 34 12](https://user-images.githubusercontent.com/7140210/107498550-3ac12380-6b94-11eb-9aa3-dc5498486d12.png)

In this example mask token is not replaced by a single BPE token, but an entire sentence and that sounds strange.
If there is something that we can do on our side, let us know.
Thanks<|||||>@simonefrancia are you referring to the third result in the screenshot?<|||||>@julien-c yes. My doubt is that input sentence is repeated for the third result.<|||||>I think it's the widget's intended behavior for BPE when we are not able to display the BPE token by itself. But we can take a look...

How are the other results, are they sensible?<|||||>I confirm it's the widget because suggested result is len <2, it's trying to repeat the full sentence instead of just the token.
And the first C is ignored because it's a `<unk>` from the tokenizer's standpoint. <|||||>I found other interesting cases, for example this one, when mask is at starting point.

![Schermata 2021-02-10 alle 11 56 35](https://user-images.githubusercontent.com/7140210/107501006-23d00080-6b97-11eb-97f8-7cfee6744b60.png)

In case we don't specify anything before `<mask>`, something goes wrong. My doubt is that in this case `<mask>` token is replaced by `<s>` token. I tried to insert `<s>` before `<mask>` token and it works.

![Schermata 2021-02-10 alle 11 53 19](https://user-images.githubusercontent.com/7140210/107500795-e4091900-6b96-11eb-91a0-851cc0015aa1.png)

Hope this can help you.
<|||||>@Narsil Ok, but is it possible to force output that would be `<unk>` (because uppercase) to lowercase, in order that `<unk>` tokens can't appear? wikipedia model is lower case, so we can force to treat only lowercase words.
Thanks<|||||>Hi @simonefrancia.
In order to force lowercase, you can do it in the Fast tokenizer but that would lead to different results between Slow and Fast tokenizers again.

> @loretoparisi if you want to actually force lowercasing input you can by changing normalizer within tokenizer.json to Sequence with a Lowercase then the precompiled_charsmap. But be aware that you won't have the same results as the raw SPM tokenizer anymore. Let me know if you want to do that I can do it, but again be careful of the impacts it could have for the model.

As for the widget, a fix is coming (it's really a display issue, if you look at the raw results it should make more sense).<|||||>I opened a new issue to keep track of the lowercasing issue as this is something that would probably be helpful for many tokenizers. (cf #10121)

I believe everything else has been fixed, has it?<|||||>I think so but I'll let @simonefrancia confirm.<|||||>for [umberto-wikipedia](https://huggingface.co/Musixmatch/umberto-wikipedia-uncased-v1) I think that's all, guys. Thanks
Instead, for [umberto-commoncrawl ](https://huggingface.co/Musixmatch/umberto-commoncrawl-cased-v1)model keeps loading. Also there are same problems in tokenizer? 


<|||||>Yes it's the same problem. Do you want me to fix it in the same way ? (Hopefully this time it works right off the bat.)

Are there any other models that could be under the same flag ? (I detected only this one during my full sweep for your organization)<|||||>For our organization, we have only two models, umberto-wikipedia ( the one you fixed) and umberto-commoncrawl ( the one to be fixed). 
Umberto commoncrawl is cased, so maybe it could be a different problem or a different way to be fixed, but we would like it works. 
thanks for your support<|||||>It's fixed now : https://huggingface.co/Musixmatch/umberto-commoncrawl-cased-v1?text=Lo+scopo+della+vita+%C3%A8+%3Cmask%3E.<|||||>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.