diff --git a/main.py b/main.py
index 2edb96e..05bcf5c 100644
--- a/main.py
+++ b/main.py
@@ -30,7 +30,10 @@ def running(local_rank, config, task, backup_config=False, setup_output_dir=Fals
         output_dir = Path(config.result_dir) / config.name if config.output_dir is None else config.output_dir
         config.output_dir = str(output_dir)
         if output_dir.exists():
-            assert not any(output_dir.iterdir()), "output_dir must be empty"
+            # assert not any(output_dir.iterdir()), "output_dir must be empty"
+            contains = list(output_dir.iterdir())
+            assert (len(contains) == 0) or (len(contains) == 1 and contains[0].name == "config.yml"), \
+                f"output_dir must by empty or only contains config.yml, but now got {len(contains)} files"
         else:
             if idist.get_rank() == 0:
                 output_dir.mkdir(parents=True)
diff --git a/run.sh b/run.sh
index d075595..21127a1 100644
--- a/run.sh
+++ b/run.sh
@@ -1,8 +1,14 @@
 #!/usr/bin/env bash
 
 CONFIG=$1
-GPUS=$2
+TASK=$2
+GPUS=$3
 
-#  CUDA_VISIBLE_DEVICES=$GPUS \
-PYTHONPATH=.:$PYTHONPATH OMP_NUM_THREADS=1 python -m torch.distributed.launch --nproc_per_node="$GPUS" \
-  main.py train "$CONFIG" --backup_config --setup_output_dir --setup_random_seed
+_command="print(len('${GPUS}'.split(',')))"
+GPU_COUNT=$(python3 -c "${_command}")
+
+echo "GPU_COUNT:${GPU_COUNT}"
+
+CUDA_VISIBLE_DEVICES=$GPUS \
+PYTHONPATH=.:$PYTHONPATH OMP_NUM_THREADS=1 python -m torch.distributed.launch --nproc_per_node="$GPU_COUNT" \
+  main.py "$TASK" "$CONFIG" --backup_config --setup_output_dir --setup_random_seed
diff --git a/util/handler.py b/util/handler.py
index db1d3d1..180b872 100644
--- a/util/handler.py
+++ b/util/handler.py
@@ -3,13 +3,13 @@ from pathlib import Path
 import torch
 
 import ignite.distributed as idist
-from ignite.engine import Events
+from ignite.engine import Events, Engine
 from ignite.handlers import Checkpoint, DiskSaver, TerminateOnNan
 from ignite.contrib.handlers import BasicTimeProfiler
 
 
 def setup_common_handlers(
-        trainer,
+        trainer: Engine,
         output_dir=None,
         stop_on_nan=True,
         use_profiler=True,
@@ -39,6 +39,11 @@ def setup_common_handlers(
     :param checkpoint_kwargs:
     :return:
     """
+    @trainer.on(Events.STARTED)
+    @idist.one_rank_only()
+    def print_dataloader_size(engine):
+        engine.logger.info(f"data loader length: {len(engine.state.dataloader)}")
+
     if stop_on_nan:
         trainer.add_event_handler(Events.ITERATION_COMPLETED, TerminateOnNan())
 
@@ -68,6 +73,8 @@ def setup_common_handlers(
         def print_interval(engine):
             print_str = f"epoch:{engine.state.epoch} iter:{engine.state.iteration}\t"
             for m in metrics_to_print:
+                if m not in engine.state.metrics:
+                    continue
                 print_str += f"{m}={engine.state.metrics[m]:.3f} "
             engine.logger.info(print_str)