When cupy is unavailable, the costvol_func.forward() now falls back to a
pure-PyTorch implementation using unfold + dot product instead of raising
a RuntimeError. The CUDA/cupy kernel path is preserved unchanged for when
cupy is available. This allows BIM-VFI to run on systems without cupy
(including CPU-only setups), matching the pattern used for the softsplat
fallbacks in SGM-VFI and GIMM-VFI.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Ethanfel
2e98e453a4