MisconfigurationException: ddp2 only works in SLURM or via torchelastic with the WORLD_SIZE, LOCAL_RANK, GROUP_RANK flags
🐛 Bug
pytorch_lightning.utilities.exceptions.MisconfigurationException: ddp2 only works in SLURM or via torchelastic with the WORLD_SIZE, LOCAL_RANK, GROUP_RANK flags
Expected behavior
Using ddp2 and 16bit training on 8 GPUs on Slurm machine causes above error. I have installed torchelastic but that didn't help.
Environment

CUDA:
- GPU:
- GeForce GTX 1080 Ti
- GeForce GTX 1080 Ti
- GeForce GTX 1080 Ti
- GeForce GTX 1080 Ti
- GeForce GTX 1080 Ti
- GeForce GTX 1080 Ti
- GeForce GTX 1080 Ti
- GeForce GTX 1080 Ti
- available:         True
- version:           9.2
Packages:
- numpy:             1.19.1
- pyTorch_debug:     True
- pyTorch_version:   1.7.0+cu92
- pytorch-lightning: 1.0.4
- tqdm:              4.50.2
System:
- OS:                Linux
- architecture:
- 64bit
-
- processor:         x86_64
- python:            3.7.4
- version:           #166-Ubuntu SMP Wed Nov 14 20:09:47 UTC 2018