When using nvdifast on multiple GPUs, lock file exists in build directory appears

[Fjzd]

When using nvdifast on multiple GPUs, lock file exists in build directory appears

[Samuli Laine]

Duplicate of #67

[Jean-Paul Ainam]

what file should I delete? ./cache/torch_extensions/nvdiffrast_plugin/lock', only the lock file or all the nvdiffrast_plugin extension?