Restore removed comments in compute_topk_scores

Signed-off-by: Allen Shen <aoshen@inferact.ai>

Author: aoshen02

vllm/v1/worker/gpu/sample/logprob.py

@@ -130,13 +130,18 @@ def compute_topk_scores(
         else:
             scores = compute_token_logprobs(logits, logprob_token_ids)
     else:
+        # Some requests specified logprob_token_ids. Build the [batch_size,
+        # 1 + max_cols] token_ids matrix and validity mask on the GPU via a
+        # single triton kernel, overriding the topk columns with per-request
+        # tokens where applicable.
         assert logprob_token_ids_state is not None
         assert expanded_idx_mapping is not None
 
         if num_logprobs > 0:
             topk_token_ids = torch.topk(logits, num_logprobs, dim=-1).indices
             topk_token_ids = topk_token_ids.to(torch.int32)
         else:
+            # This tensor just used as an int32 pointer, data not accessed.
             topk_token_ids = logprob_token_ids_state.token_ids.gpu
 
         num_cols = max(num_logprobs, max_per_req_token_ids)