In this example we want to optimize a nonlinear constraint problem. Instead of just getting a final number from a black-box routine, we want to look at the constraints and visualize partial solutions. The following problem is described by Rakesh Angira and B.V. Babu in section 6 of the paper "Optimization of Non-Linear Chemical Processes using Modified Differential Evolution" ( http://discovery.bits-pilani.ac.in/~bvbabu/RB_IICAI-05_147.pdf). The goal is to determine the optimal operation of an alkylation unit, commonly used in the petroleum industry.