Fix reader bug.

fluid/object_detection/train.py

@@ -174,6 +174,9 @@ def parallel_exe(args,
     elif data_args.dataset == 'pascalvoc':
         num_classes = 21
 
+    devices = os.getenv("CUDA_VISIBLE_DEVICES") or ""
+    devices_num = len(devices.split(","))
+
     image = fluid.layers.data(name='image', shape=image_shape, dtype='float32')
     gt_box = fluid.layers.data(
         name='gt_box', shape=[4], dtype='float32', lod_level=1)
@@ -253,6 +256,7 @@ def parallel_exe(args,
         for batch_id, data in enumerate(train_reader()):
             prev_start_time = start_time
             start_time = time.time()
+            if len(data) < devices_num: continue
             loss_v, = train_exe.run(fetch_list=[loss.name],
                                    feed_dict=feeder.feed(data))
             end_time = time.time()