Potential bug in metric when updated with a slice of tensor in DDP
🐛 Bug

when a metric is updated with a slice of tensor as one of the inputs (either pred or target) with multiple GPU with DDP, it throws out an error:
RuntimeError: Tensors must be non-overlapping and dense

Once the slice of the tensor is clone and detach, then it works.
Please reproduce using [the BoringModel and post here]
The issue can be reproduced below:
https://colab.research.google.com/drive/1yuqwb8BHhmDATp2IUNRNjSXOg3kV73Wp?usp=sharing

To Reproduce

Expected behavior
the metric update should work with a slice of tensor

Environment
CUDA:
- GPU:
- Tesla P100-PCIE-16GB
- available:         True
- version:           10.1

Packages:

numpy:             1.18.5
pyTorch_debug:     True
pyTorch_version:   1.7.0+cu101
pytorch-lightning: 1.0.7
tqdm:              4.41.1


System:

OS:                Linux
architecture:

64bit



processor:         x86_64
python:            3.6.9
version:           #1 SMP Thu Jul 23 08:00:38 PDT 2020



Additional context