Dynamo DDP accuracy bench uses find_unused_parameters (#88645)
- find_unused_parameters adds a slight overhead, but is required
in cases where users do not manually specify parameters to ignore
which will not receive grads. In some models, some parameters
do not receive grads, and this causes DDP to throw an exception
as it waits for a grad for each parameter
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88645
Approved by: https://github.com/soumith
