Allow CLIP loss to be used with models that have logit bias

Author: rwightman

src/open_clip/loss.py

@@ -101,7 +101,7 @@ def get_ground_truth(self, device, num_logits) -> torch.Tensor:
             labels = self.labels[device]
         return labels
 
-    def get_logits(self, image_features, text_features, logit_scale):
+    def get_logits(self, image_features, text_features, logit_scale, logit_bias=None):
         if self.world_size > 1:
             all_image_features, all_text_features = gather_features(
                 image_features,
@@ -122,10 +122,21 @@ def get_logits(self, image_features, text_features, logit_scale):
         else:
             logits_per_image = logit_scale * image_features @ text_features.T
             logits_per_text = logit_scale * text_features @ image_features.T
-        
+
+        if logit_bias is not None:
+            logits_per_image += logit_bias
+            logits_per_text += logit_bias
+
         return logits_per_image, logits_per_text
 
-    def forward(self, image_features, text_features, logit_scale, output_dict=False):
+    def forward(
+            self,
+            image_features,
+            text_features,
+            logit_scale,
+            logit_bias=None,
+            output_dict=False,
+    ):
         device = image_features.device
         logits_per_image, logits_per_text = self.get_logits(image_features, text_features, logit_scale)