Fix division by zero in Hits@k metric by checking for length

Fixes pyg-team#9936

torch_geometric/nn/kge/base.py

@@ -18,6 +18,7 @@ class KGEModel(torch.nn.Module):
         sparse (bool, optional): If set to :obj:`True`, gradients w.r.t. to the
             embedding matrices will be sparse. (default: :obj:`False`)
     """
+
     def __init__(
         self,
         num_nodes: int,
@@ -123,15 +124,19 @@ def test(
             tail_indices = torch.arange(self.num_nodes, device=t.device)
             for ts in tail_indices.split(batch_size):
                 scores.append(self(h.expand_as(ts), r.expand_as(ts), ts))
-            rank = int((torch.cat(scores).argsort(
-                descending=True) == t).nonzero().view(-1))
+            rank = int(
+                (torch.cat(scores).argsort(descending=True) == t).nonzero().view(-1)
+            )
             mean_ranks.append(rank)
             reciprocal_ranks.append(1 / (rank + 1))
             hits_at_k.append(rank < k)
 
         mean_rank = float(torch.tensor(mean_ranks, dtype=torch.float).mean())
         mrr = float(torch.tensor(reciprocal_ranks, dtype=torch.float).mean())
-        hits_at_k = int(torch.tensor(hits_at_k).sum()) / len(hits_at_k)
+        if len(hits_at_k) == 0:
+            hits_at_k = 0.0
+        else:
+            hits_at_k = int(torch.tensor(hits_at_k).sum()) / len(hits_at_k)
 
         return mean_rank, mrr, hits_at_k
 
@@ -152,8 +157,9 @@ def random_sample(
         """
         # Random sample either `head_index` or `tail_index` (but not both):
         num_negatives = head_index.numel() // 2
-        rnd_index = torch.randint(self.num_nodes, head_index.size(),
-                                  device=head_index.device)
+        rnd_index = torch.randint(
+            self.num_nodes, head_index.size(), device=head_index.device
+        )
 
         head_index = head_index.clone()
         head_index[:num_negatives] = rnd_index[:num_negatives]
@@ -163,6 +169,8 @@ def random_sample(
         return head_index, rel_type, tail_index
 
     def __repr__(self) -> str:
-        return (f'{self.__class__.__name__}({self.num_nodes}, '
-                f'num_relations={self.num_relations}, '
-                f'hidden_channels={self.hidden_channels})')
+        return (
+            f"{self.__class__.__name__}({self.num_nodes}, "
+            f"num_relations={self.num_relations}, "
+            f"hidden_channels={self.hidden_channels})"
+        )