ultralytics 8.1.39 add YOLO-World training (#9268)

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>
Co-authored-by: UltralyticsAssistant <web@ultralytics.com>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/models/yolo/world/train.py

@@ -0,0 +1,91 @@
+# Ultralytics YOLO 🚀, AGPL-3.0 license
+
+from ultralytics.models import yolo
+from ultralytics.nn.tasks import WorldModel
+from ultralytics.utils import DEFAULT_CFG, RANK
+from ultralytics.data import build_yolo_dataset
+from ultralytics.utils.torch_utils import de_parallel
+from ultralytics.utils.checks import check_requirements
+import itertools
+
+try:
+    import clip
+except ImportError:
+    check_requirements("git+https://github.com/ultralytics/CLIP.git")
+    import clip
+
+
+def on_pretrain_routine_end(trainer):
+    """Callback."""
+    if RANK in (-1, 0):
+        # NOTE: for evaluation
+        names = [name.split("/")[0] for name in list(trainer.test_loader.dataset.data["names"].values())]
+        de_parallel(trainer.ema.ema).set_classes(names, cache_clip_model=False)
+    device = next(trainer.model.parameters()).device
+    text_model, _ = clip.load("ViT-B/32", device=device)
+    for p in text_model.parameters():
+        p.requires_grad_(False)
+    trainer.text_model = text_model
+
+
+class WorldTrainer(yolo.detect.DetectionTrainer):
+    """
+    A class to fine-tune a world model on a close-set dataset.
+
+    Example:
+        ```python
+        from ultralytics.models.yolo.world import WorldModel
+
+        args = dict(model='yolov8s-world.pt', data='coco8.yaml', epochs=3)
+        trainer = WorldTrainer(overrides=args)
+        trainer.train()
+        ```
+    """
+
+    def __init__(self, cfg=DEFAULT_CFG, overrides=None, _callbacks=None):
+        """Initialize a WorldTrainer object with given arguments."""
+        if overrides is None:
+            overrides = {}
+        super().__init__(cfg, overrides, _callbacks)
+
+    def get_model(self, cfg=None, weights=None, verbose=True):
+        """Return WorldModel initialized with specified config and weights."""
+        # NOTE: This `nc` here is the max number of different text samples in one image, rather than the actual `nc`.
+        # NOTE: Following the official config, nc hard-coded to 80 for now.
+        model = WorldModel(
+            cfg["yaml_file"] if isinstance(cfg, dict) else cfg,
+            ch=3,
+            nc=min(self.data["nc"], 80),
+            verbose=verbose and RANK == -1,
+        )
+        if weights:
+            model.load(weights)
+        self.add_callback("on_pretrain_routine_end", on_pretrain_routine_end)
+
+        return model
+
+    def build_dataset(self, img_path, mode="train", batch=None):
+        """
+        Build YOLO Dataset.
+
+        Args:
+            img_path (str): Path to the folder containing images.
+            mode (str): `train` mode or `val` mode, users are able to customize different augmentations for each mode.
+            batch (int, optional): Size of batches, this is for `rect`. Defaults to None.
+        """
+        gs = max(int(de_parallel(self.model).stride.max() if self.model else 0), 32)
+        return build_yolo_dataset(
+            self.args, img_path, batch, self.data, mode=mode, rect=mode == "val", stride=gs, multi_modal=mode == "train"
+        )
+
+    def preprocess_batch(self, batch):
+        """Preprocesses a batch of images for YOLOWorld training, adjusting formatting and dimensions as needed."""
+        batch = super().preprocess_batch(batch)
+
+        # NOTE: add text features
+        texts = list(itertools.chain(*batch["texts"]))
+        text_token = clip.tokenize(texts).to(batch["img"].device)
+        txt_feats = self.text_model.encode_text(text_token).to(dtype=batch["img"].dtype)  # torch.float32
+        txt_feats = txt_feats / txt_feats.norm(p=2, dim=-1, keepdim=True)
+        batch["txt_feats"] = txt_feats.reshape(len(batch["texts"]), -1, txt_feats.shape[-1])
+        return batch