fix bug

ppsci/utils/symbolic.py

@@ -933,35 +933,38 @@ def _expr_to_callable_nodes(
                 fused_node_seq, list
             ), "'fused_node_seq' should be list of 'FusedDerivativeNode'"
             gid0, nid0 = candidate_pos[0]
-            logger.debug(
+            print(
                 f"Fused {len(candidate_pos)} derivatives nodes: "
                 f"{[callable_nodes_group[i][j].expr for i, j in candidate_pos]} into"
                 f" fuse node sequence: {fused_node_seq} at position: ([{gid0}][{nid0}])"
             )
 
+            # mark merged node
+            for i, (gid, nid) in enumerate(candidate_pos):
+                assert isinstance(callable_nodes_group[gid][nid], DerivativeNode)
+                callable_nodes_group[gid][nid].merged = True
+
             # replace first mergable node with fused node sequence(packed in list)
             # then mask the rest merged node to None(except [gid0, nid0])
-            for i, (gid, nid) in enumerate(candidate_pos):
+            for i, (gid, nid) in enumerate(candidate_pos[1:]):
                 # keep the end node of each group to avoid generating empty callable
                 # node sequence, this will not effect performance since cache strategy
                 # in Node.forward
-                callable_nodes_group[gid][nid].merged = True
-                if i == 0:
-                    if nid0 == len(callable_nodes_group[gid0]) - 1:
-                        callable_nodes_group[gid0].insert(nid0, fused_node_seq)
-                    else:
-                        callable_nodes_group[gid0] = fused_node_seq
-                else:
-                    if nid != len(callable_nodes_group[gid]) - 1:
-                        callable_nodes_group[gid][nid] = None
+                if nid != len(callable_nodes_group[gid]) - 1:
+                    callable_nodes_group[gid][nid] = None
+
+            if nid0 == len(callable_nodes_group[gid0]) - 1:
+                callable_nodes_group[gid0].insert(nid0, fused_node_seq)
+            else:
+                callable_nodes_group[gid0][nid0] = fused_node_seq
 
             # re-organize callable_nodes_group, remove None element and unpack list
             for i in range(len(callable_nodes_group)):
                 tmp = []
                 for j in range(len(callable_nodes_group[i])):
-                    if isinstance(
-                        callable_nodes_group[i][j], (Node, FusedDerivativeNode)
-                    ):
+                    if isinstance(callable_nodes_group[i][j], Node):
+                        tmp.append(callable_nodes_group[i][j])
+                    elif isinstance(callable_nodes_group[i][j], FusedDerivativeNode):
                         tmp.append(callable_nodes_group[i][j])
                     elif isinstance(callable_nodes_group[i][j], list) and isinstance(
                         callable_nodes_group[i][j][0], FusedDerivativeNode
@@ -971,7 +974,8 @@ def _expr_to_callable_nodes(
                         assert (
                             callable_nodes_group[i][j] is None
                         ), f"Unexpected element: {callable_nodes_group[i][j]}"
-                callable_nodes_group[i] = tmp
+                callable_nodes_group[i] = [t for t in tmp]
+
         else:
             # exit while loop if no more fused
             break