For the algorithm, the evaluation of the map described in Equation ( ) is crucial. It must be possible to evaluate this map reliably and fast on a large range of optimization variables x opt . Therefore, the optimization variables and the mapping to all process variables have to be chosen carefully. In the following Subsection 3.1, we will describe how to compute all process variables knowing the values for the streams that connect the column sections C i,j in the Petlyuk sequence discussed in Section 2 and shown in Figure for the example of a column with two dividing walls. In Subsection 3.2 we will then introduce conditions under which this procedure is guaranteed to succeed. Thus, a suitable choice of optimization variables for multiple dividing wall columns are variables that describe the interconnecting streams of the corresponding Petlyuk sequence.