Refactor new model.warmup() method (#5810)

* Refactor new `model.warmup()` method

* Add half

detect.py

@@ -97,8 +97,7 @@ def run(weights=ROOT / 'yolov5s.pt',  # model.pt path(s)
     vid_path, vid_writer = [None] * bs, [None] * bs
 
     # Run inference
-    if pt and device.type != 'cpu':
-        model(torch.zeros(1, 3, *imgsz).to(device).type_as(next(model.model.parameters())))  # warmup
+    model.warmup(imgsz=(1, 3, *imgsz), half=half)  # warmup
     dt, seen = [0.0, 0.0, 0.0], 0
     for path, im, im0s, vid_cap, s in dataset:
         t1 = time_sync()