torch.empty() for speed improvements (#9025)

`torch.empty()` for speed improvement

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

utils/autobatch.py

@@ -47,7 +47,7 @@ def autobatch(model, imgsz=640, fraction=0.9, batch_size=16):
     # Profile batch sizes
     batch_sizes = [1, 2, 4, 8, 16]
     try:
-        img = [torch.zeros(b, 3, imgsz, imgsz) for b in batch_sizes]
+        img = [torch.empty(b, 3, imgsz, imgsz) for b in batch_sizes]
         results = profile(img, model, n=3, device=device)
     except Exception as e:
         LOGGER.warning(f'{prefix}{e}')