find lookup table in order (#20932)

test=develop

python/paddle/fluid/incubate/fleet/parameter_server/pslib/optimizer_factory.py

@@ -130,13 +130,22 @@ class DistributedAdam(DistributedOptimizerImplBase):
         find multi-sparse-table
         """
         table_names = set()
+        cnt = 0
+        tmp_list = []
+        ret_list = []
         for loss in losses:
             for op in loss.block.program.global_block().ops:
                 if op.type == "lookup_table":
                     if op.attr('is_distributed') is True:
                         table_name = op.input("W")[0]
+                        if table_name not in table_names:
                             table_names.add(table_name)
-        return list(table_names)
+                            tmp_list.append([table_name, cnt])
+                            cnt += 1
+        tmp_list.sort(key=lambda k: k[1])
+        for x in tmp_list:
+            ret_list.append(x[0])
+        return ret_list
 
     def _minimize(self,
                   losses,