ddp with subprocess does not work with hydra
Thanks for the great work.
The recent change replaced .spawn with subprocess which forces pass "--gpus" flag. This works fine for the project using argparse to parse arguments. But it does not work with hydra since the arguments in hydra are passed like "gpus=2" not "--gpus 2". The "--somearg val" in hydra is used for specific purpose not for arguments passing.
Could you please provide the support for hydra under the new context?
Thanks.

  
    
      pytorch-lightning/pytorch_lightning/trainer/distrib_data_parallel.py
    
    
        Lines 370 to 372
      in
      82a2029
    
  
  
    

        
          
           if '--gpus' not in command: 
        

        
          
               arg_gpus = len(self.gpus) if isinstance(self.gpus, list) else self.gpus 
        

        
          
               command += ['--gpus', arg_gpus]