<p>In <a href="https://github.com/mlpack/mlpack/pull/451#discussion_r40670241">src/mlpack/methods/ann/activation_functions/lazy_logistic_function.hpp</a>:</p>
<pre style='color:#555'>&gt; + * f^{-1}(y) &amp;=&amp; ln(\frac{y}{1-y})
&gt; + * @f}
&gt; + */
&gt; +class LazyLogisticFunction
&gt; +{
&gt; +  public:
&gt; +  /**
&gt; +   * Computes the logistic function without checking overflow or underflow
&gt; +   *
&gt; +   * @param x Input data.
&gt; +   * @param y The resulting output activation.
&gt; +   */
&gt; +  template&lt;typename InputVecType, typename OutputVecType&gt;
&gt; +  static void fn(const InputVecType&amp; x, OutputVecType&amp; y)
&gt; +  {
&gt; +    y = (1.0 / (1 + arma::exp(-x)));
</pre>
<p>I am totally fine with that</p>

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