openvino/docs/ops/activation/LogSoftmax_5.md

LogSoftMax

Versioned name: LogSoftmax-5

Category: Activation

Short description: LogSoftmax computes the natural logarithm of softmax values for the given input.

Note: This is recommended to not compute LogSoftmax directly as Log(Softmax(x, axis)), more numeric stable is to compute LogSoftmax as: \f[ t = (x - ReduceMax(x, axis)) \ LogSoftmax(x, axis) = t - Log(ReduceSum(Exp(t), axis)) \f]

Attributes

• axis

  • Description: axis represents the axis of which the LogSoftmax is calculated. Negative value means counting dimensions from the back.
  • Range of values: any integer value
  • Type: int
  • Default value: 1
  • Required: no

Inputs:

• 1: Input tensor x of type T with enough number of dimension to be compatible with axis attribute. Required.

Outputs:

• 1: The resulting tensor of the same shape and of type T.

Types

• T: any floating point type.

Mathematical Formulation

\f[ y_{c} = ln\left(\frac{e^{Z_{c}}}{\sum_{d=1}^{C}e^{Z_{d}}}\right) \f] where \f$C\f$ is a size of tensor along axis dimension.

Example

<layer ... type="LogSoftmax" ... >
    <data axis="1" />
    <input>
        <port id="0">
            <dim>256</dim>
            <dim>56</dim>
        </port>
    </input>
    <output>
        <port id="3">
            <dim>256</dim>
            <dim>56</dim>
        </port>
    </output>
</layer>