老师您好，在第二种情况，多机cpu训练的情况下程序一直在等待，
To enable them in other operations, rebuild TensorFlow with the appropriate compiler flags.
2021-03-26 14:49:55.649453: I tensorflow/compiler/jit/xla_gpu_device.cc:99] Not creating XLA devices, tf_xla_enable_xla_devices not set
2021-03-26 14:49:55.661519: I tensorflow/compiler/jit/xla_gpu_device.cc:99] Not creating XLA devices, tf_xla_enable_xla_devices not set
2021-03-26 14:49:55.685741: I tensorflow/core/distributed_runtime/rpc/grpc_channel.cc:301] Initialize GrpcChannelCache for job ps → {0 → localhost:2222}
2021-03-26 14:49:55.696396: I tensorflow/core/distributed_runtime/rpc/grpc_channel.cc:301] Initialize GrpcChannelCache for job worker → {0 → localhost:2223, 1 → localhost:2224}
2021-03-26 14:49:55.707198: I tensorflow/core/distributed_runtime/rpc/grpc_server_lib.cc:411] Started server with target: grpc://localhost:2224
WARNING:tensorflow:Enabled NCCL communication but no GPUs detected/specified.
这是什么原因啊