From e30514922b5236f9e61985b19cae239b27eb34f1 Mon Sep 17 00:00:00 2001
From: William Falcon <falc@fb.com>
Date: Wed, 7 Aug 2019 13:43:28 -0400
Subject: [PATCH] added single gpu train test

---
 pytorch_lightning/models/trainer.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pytorch_lightning/models/trainer.py b/pytorch_lightning/models/trainer.py
index b0ce3d1a..69c7a3e8 100644
--- a/pytorch_lightning/models/trainer.py
+++ b/pytorch_lightning/models/trainer.py
@@ -196,7 +196,7 @@ class Trainer(TrainerIO):
                 warnings.warn(w)
 
         # remove dp and ddp when requesting single gpu
-        if len(self.data_parallel_device_ids) == 1:
+        if self.data_parallel_device_ids is not None and len(self.data_parallel_device_ids) == 1:
             self.use_ddp = False
             self.use_dp = False
             self.single_gpu = True