fix dist eval (#364)

tools/eval.py

@@ -59,9 +59,14 @@ def main(args, return_dict={}):
 
     paddle.disable_static(place)
 
-    strategy = paddle.distributed.init_parallel_env()
+    use_data_parallel = int(os.getenv("PADDLE_TRAINERS_NUM", 1)) != 1
+    config["use_data_parallel"] = use_data_parallel
+
     net = program.create_model(config.ARCHITECTURE, config.classes_num)
-    net = paddle.DataParallel(net, strategy)
+    if config["use_data_parallel"]:
+        strategy = paddle.distributed.init_parallel_env()
+        net = paddle.DataParallel(net, strategy)
+
     init_model(config, net, optimizer=None)
     valid_dataloader = Reader(config, 'valid', places=place)()
     net.eval()