title: Gini Coefficient parallel/streaming implementation with unsorted input
body: <p>Is there a streaming implementation to compute the Gini Coefficient (not to be confused with the Gini Impurity used in decision trees induction) of an unsorted input?</p>
  <p>Currently, I am aware of two implementation for the Gini Coefficient:</p>
  <ul>
  <li>One requires a sorted input and basically computes the Area Under the Lorenz Curve first and the ratio later</li>
  <li>Another requires an all pairs comparison of all the inputs (whether the input is sorted or not)</li>
  </ul>
  <p>Is there a way to avoid sorting the input and also an n^2 all pairs comparison?</p>