Weird-ish: Not creating unique caches for different phases
MEMBER
Looks like a duplicate of #120.
This is already fixed on master. We'll do a new release on pypi soon
2020-05-23T11:09:30Z
https://github.com/huggingface/datasets/issues/186#issuecomment-633028562
https://api.github.com/repos/huggingface/datasets/issues/186
MDEyOklzc3VlQ29tbWVudDYzMzAyODU2Mg==
https://api.github.com/repos/huggingface/datasets/issues/comments/633028562/reactions
2020-05-23T11:09:30Z
https://api.github.com/repos/huggingface/datasets/issues/comments/633028562
https://avatars.githubusercontent.com/u/42851186?v=4
https://api.github.com/users/lhoestq/events{/privacy}
https://api.github.com/users/lhoestq/followers
https://api.github.com/users/lhoestq/following{/other_user}
https://api.github.com/users/lhoestq/gists{/gist_id}
https://github.com/lhoestq
lhoestq
MDQ6VXNlcjQyODUxMTg2
https://api.github.com/users/lhoestq/orgs
https://api.github.com/users/lhoestq/received_events
https://api.github.com/users/lhoestq/repos
https://api.github.com/users/lhoestq/starred{/owner}{/repo}
https://api.github.com/users/lhoestq/subscriptions
User
https://api.github.com/users/lhoestq
public
NONE
Good catch, it looks fixed.

2020-05-23T20:22:17Z
https://github.com/huggingface/datasets/issues/186#issuecomment-633132525
https://api.github.com/repos/huggingface/datasets/issues/186
MDEyOklzc3VlQ29tbWVudDYzMzEzMjUyNQ==
https://api.github.com/repos/huggingface/datasets/issues/comments/633132525/reactions
2020-05-23T20:22:17Z
https://api.github.com/repos/huggingface/datasets/issues/comments/633132525
https://avatars.githubusercontent.com/u/1668462?v=4
https://api.github.com/users/zphang/events{/privacy}
https://api.github.com/users/zphang/followers
https://api.github.com/users/zphang/following{/other_user}
https://api.github.com/users/zphang/gists{/gist_id}
https://github.com/zphang
zphang
MDQ6VXNlcjE2Njg0NjI=
https://api.github.com/users/zphang/orgs
https://api.github.com/users/zphang/received_events
https://api.github.com/users/zphang/repos
https://api.github.com/users/zphang/starred{/owner}{/repo}
https://api.github.com/users/zphang/subscriptions
User
https://api.github.com/users/zphang
public
Sample code:

```python
import nlp
dataset = nlp.load_dataset('boolq')

def func1(x):
    return x

def func2(x):
    return None

train_output = dataset["train"].map(func1)
valid_output = dataset["validation"].map(func1)
print()
print(len(train_output), len(valid_output))
# Output: 9427 9427
```

The map method in both cases seem to be pointing to the same cache, so the latter call based on the validation data will return the processed train data cache.

What's weird is that the following doesn't seem to be an issue:

```python
train_output = dataset["train"].map(func2)
valid_output = dataset["validation"].map(func2)
print()
print(len(train_output), len(valid_output))
# 9427 3270
```