SoftMax.cs

usingSystem;

namespaceAlgorithms.Numeric;

/// <summary>
/// Implementation of the SoftMax function.
/// Its a function that takes as input a vector of K real numbers, and normalizes
/// it into a probability distribution consisting of K probabilities proportional
/// to the exponentials of the input numbers. After softmax, the elements of the vector always sum up to 1.
/// https://en.wikipedia.org/wiki/Softmax_function.
/// </summary>
publicstaticclassSoftMax
{
/// <summary>
/// Compute the SoftMax function.
/// The SoftMax function is defined as:
/// softmax(x_i) = exp(x_i) / sum(exp(x_j)) for j = 1 to n
/// where x_i is the i-th element of the input vector.
/// The elements of the output vector are the probabilities of the input vector, the output sums up to 1.
/// </summary>
/// <param name="input">The input vector of real numbers.</param>
/// <returns>The output vector of real numbers.</returns>
publicstaticdouble[]Compute(double[]input)
{
if(input.Length==0)
{
thrownewArgumentException("Array is empty.");
}

varexponentVector=newdouble[input.Length];
varsum=0.0;
for(varindex=0;index<input.Length;index++)
{
exponentVector[index]=Math.Exp(input[index]);
sum+=exponentVector[index];
}

for(varindex=0;index<input.Length;index++)
{
exponentVector[index]/=sum;
}

returnexponentVector;
}
}