fix the last bug hopefully.

Author: mfbalin

python/dgl/graphbolt/impl/cooperative_conv.py

@@ -47,11 +47,12 @@ def forward(
                 (sum(counts_sent.get(ntype, [0])),) + typed_tensor.shape[1:],
                 requires_grad=typed_tensor.requires_grad,
             )
+            default_splits = [0] * torch.distributed.get_world_size()
             all_to_all(
-                torch.split(out, counts_sent.get(ntype, 0)),
+                torch.split(out, counts_sent.get(ntype, default_splits)),
                 torch.split(
                     typed_tensor[seed_inverse_ids.get(ntype, slice(None))],
-                    counts_received.get(ntype, 0),
+                    counts_received.get(ntype, default_splits),
                 ),
             )
             outs[ntype] = out