Convex programming with fast proximal and linear operators

We present Epsilon, a system for general convex programming using fast linear and proximal operators. As with existing convex programming frameworks, users specify convex optimization problems using a natural grammar for mathematical expressions, composing functions in a way that is guaranteed to be convex by the rules of disciplined convex programming. Given such an input, the Epsilon compiler transforms the optimization problem into a mathematically equivalent form consisting only of functions with efficient proximal operators---an intermediate representation we refer to as prox-affine form. By reducing problems to this form, Epsilon enables solving general convex problems using a large library of fast proximal and linear operators; numerical examples on many popular problems from statistics and machine learning show that this often improves running times by an order of magnitude or more vs. existing approaches based on conic solvers.