Warning for CLIP Score on long captions

CHANGELOG.md

@@ -35,6 +35,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added argument `extended_summary` to `MeanAveragePrecision` such that precision, recall, iou can be easily returned ([#1983](https://github.com/Lightning-AI/torchmetrics/pull/1983))
 
 
+- Added warning to `ClipScore` if long captions are detected and truncate ([#2001](https://github.com/Lightning-AI/torchmetrics/pull/2001))
+
+
 ### Changed
 
 -

src/torchmetrics/functional/multimodal/clip_score.py

@@ -17,6 +17,7 @@
 from torch import Tensor
 from typing_extensions import Literal
 
+from torchmetrics.utilities import rank_zero_warn
 from torchmetrics.utilities.checks import _SKIP_SLOW_DOCTEST, _try_proceed_with_timeout
 from torchmetrics.utilities.imports import _TRANSFORMERS_GREATER_EQUAL_4_10
 
@@ -65,6 +66,17 @@ def _clip_score_update(
     img_features = model.get_image_features(processed_input["pixel_values"].to(device))
     img_features = img_features / img_features.norm(p=2, dim=-1, keepdim=True)
 
+    max_position_embeddings = model.config.text_config.max_position_embeddings
+    if processed_input["attention_mask"].shape[-1] > max_position_embeddings:
+        rank_zero_warn(
+            f"Encountered caption longer than {max_position_embeddings=}. Will truncate captions to this length."
+            "If longer captions are needed, initialize argument `model_name_or_path` with a model that supports"
+            "longer sequences",
+            UserWarning,
+        )
+        processed_input["attention_mask"] = processed_input["attention_mask"][..., :max_position_embeddings]
+        processed_input["input_ids"] = processed_input["input_ids"][..., :max_position_embeddings]
+
     txt_features = model.get_text_features(
         processed_input["input_ids"].to(device), processed_input["attention_mask"].to(device)
     )

tests/unittests/multimodal/test_clip_score.py

@@ -127,3 +127,15 @@ def test_plot_method(self, inputs, model_name_or_path):
         fig, ax = metric.plot()
         assert isinstance(fig, plt.Figure)
         assert isinstance(ax, matplotlib.axes.Axes)
+
+    @skip_on_connection_issues()
+    def test_warning_on_long_caption(self, inputs, model_name_or_path):
+        """Test that warning is given on long captions but metric still works."""
+        metric = CLIPScore(model_name_or_path=model_name_or_path)
+        preds, target = inputs
+        target[0] = [target[0][0], "A 28-year-old chef who recently moved to San Francisco was found dead. " * 100]
+        with pytest.warns(
+            UserWarning,
+            match="Encountered caption longer than max_position_embeddings=77. Will truncate captions to this length.*",
+        ):
+            metric.update(preds[0], target[0])