fix transpiler error

python/paddle/fluid/transpiler/distribute_transpiler.py

@@ -187,12 +187,17 @@ class DistributeTranspiler:
 
         param_list = []
         grad_list = []
+        param_grad_set = set()
         for p, g in self.params_grads:
             # skip parameter marked not trainable
             if type(p) == Parameter and p.trainable == False:
                 continue
+            if p.name not in param_grad_set:
                 param_list.append(p)
+                param_grad_set.add(p.name)
+            if g.name not in param_grad_set:
                 grad_list.append(g)
+                param_grad_set.add(g.name)
 
         self._update_dist_lookup_table_vars(param_list, grad_list,
                                             self.params_grads)
@@ -829,6 +834,9 @@ class DistributeTranspiler:
             if not block_map.has_key(varname):
                 block_map[varname] = []
             block_map[varname].append((long(offset), long(size)))
+        # Do not remove this important debug message:
+        print("block map: %s" % block_map)
+
         for varname, splited in block_map.iteritems():
             orig_var = program.global_block().var(varname)
             if len(splited) == 1: