Merge pull request #4774 from zhiqiu/dev/fix_infer2

add no_grad for infer function

tools/infer_det.py

@@ -53,6 +53,7 @@ def draw_det_res(dt_boxes, config, img, img_name, save_path):
         logger.info("The detected Image saved in {}".format(save_path))
 
 
+@paddle.no_grad()
 def main():
     global_config = config['Global']