【Ubuntu-Tensorflow】InvalidArgumentErrorGPU不能使用的问题

问题内容如下

InvalidArgumentError (see above for traceback): Cannot assign a device to node 'train/final/fc3/b/Momentum': Could not satisfy explicit device specification '/device:GPU:0' because no devices matching that specification are registered in this process; available devices: /job:localhost/replica:0/task:0/cpu:0
Colocation Debug Info:
Colocation group had the following types and devices: 
ApplyMomentum: CPU 
Mul: CPU 
Sum: CPU 
Abs: CPU 
Const: CPU 
Assign: CPU 
Identity: CPU 
VariableV2: CPU 
     [[Node: train/final/fc3/b/Momentum = VariableV2[_class=["loc:@train/final/fc3/b"], cOntainer="", dtype=DT_FLOAT, shape=[29], shared_name="", _device="/device:GPU:0"]()]]

问题原因：有些tf.Variable()不允许在GPU运行，需要在CPU运行
解决办法：修改配置里面的allow_soft_placement=True，而allow_soft_placement=True，就是运行在出现不允许在GPU运行的时候，可以切换到CPU运行。