fix windows CPU envs (#315)

demo/slimfacenet/train_eval.py

@@ -151,9 +151,9 @@ def train(exe, train_program, train_out, test_program, test_out, args):
 
 def build_program(program, startup, args, is_train=True):
     if args.use_gpu:
-        num_trainers = len(os.getenv('CUDA_VISIBLE_DEVICES').split(','))
+        num_trainers = fluid.core.get_cuda_device_count()
     else:
-        num_trainers = 1
+        num_trainers = int(os.environ.get('CPU_NUM', 1))
     places = fluid.cuda_places() if args.use_gpu else fluid.CPUPlace()
 
     train_dataset = CASIA_Face(root=args.train_data_dir)
@@ -302,9 +302,9 @@ def main():
     args = parser.parse_args()
 
     if args.use_gpu:
-        num_trainers = len(os.getenv('CUDA_VISIBLE_DEVICES').split(','))
+        num_trainers = fluid.core.get_cuda_device_count()
     else:
-        num_trainers = 1
+        num_trainers = int(os.environ.get('CPU_NUM', 1))
     print(args)
     print('num_trainers: {}'.format(num_trainers))
     if args.save_ckpt == None: