Optimize MiniCPMO mask creation with vectorized implementation (#22464)

Signed-off-by: zitian.zhao <zitian.zhao@tencentmusic.com>
Signed-off-by: zitian zhao <zitian.zhao@tencentmusic.com>

vllm/model_executor/models/minicpmo.py

@@ -587,15 +587,29 @@ class MiniCPMO(MiniCPMV2_6):
         num_lookhead: int = 0,
     ) -> torch.Tensor:
         ret = torch.zeros(size, size, device=device, dtype=torch.bool)
-        for i in range(size):
+        # Vectorized computation of row indices and chunk boundaries
+        row_indices = torch.arange(size, device=device)
+        chunk_indices = row_indices // chunk_size  
         if num_left_chunks < 0:
-                start = 0
+            # If num_left_chunks < 0, start is always 0 for all rows
+            start_indices = torch.zeros_like(row_indices)
         else:
-                start = max((i // chunk_size - num_left_chunks) * chunk_size,
-                            0)
-            ending = min((i // chunk_size + 1) * chunk_size + num_lookhead,
-                         size)
-            ret[i, start:ending] = True
+            # Compute start indices vectorially
+            start_chunk_indices = torch.clamp(chunk_indices - num_left_chunks,
+                                              min=0)
+            start_indices = start_chunk_indices * chunk_size    
+        # Compute ending indices vectorially
+        end_chunk_indices = chunk_indices + 1
+        end_indices = torch.clamp(end_chunk_indices * chunk_size +
+                                  num_lookhead,
+                                  max=size)
+        # Create column indices for broadcasting
+        col_indices = torch.arange(size, device=device).unsqueeze(0)
+        row_indices = row_indices.unsqueeze(1)
+        start_indices = start_indices.unsqueeze(1)
+        end_indices = end_indices.unsqueeze(1)
+        # Vectorized mask creation
+        ret = (col_indices >= start_indices) & (col_indices < end_indices)
         return ret
 
     def _get_feat_extract_output_lengths(self,