tf.nn.softmax(logits, dim=-1, name=None)
Docstring:
Computes softmax activations （softmax可以直接看作成激活函数，得到属于各类别的概率）
Type: function
For each batch i and class j we have
softmax = exp(logits) / reduce_sum(exp(logits), dim)
Args:
logits: A non-empty Tensor. Must be one of the following types: half, float32, float64.
dim: The dimension softmax would be performed on. The default is -1 which indicates the last dimension.
name: A name for the operation (optional).
Returns:
A Tensor. Has the same type as logits. Same shape as logits.
Raises :
InvalidArgumentError: if logits is empty or dim is beyond the last dimension of logits.
