title: Logistic regression python solvers' definitions
body: <p>I am using the logistic regression function from sklearn, and was wondering what each of the solver is actually doing behind the scenes to solve the optimization problem.</p>
  <p>Can someone briefly describe what &quot;newton-cg&quot;, &quot;sag&quot;, &quot;lbfgs&quot; and &quot;liblinear&quot; are doing?</p>