This approach allows us to represent for example each drug candidate as a node n in a graph G (see Figure ). Next, each potential FE calculation comparing two molecules is represented by an edge e in G. The estimated difficulty of calculating a well converged and accurate ∆∆G bind is represented by a score between 0 and 1 that is assigned to an e as a weight. By convention, 1 is a good score (expressing a likely accurate and well converged result) and 0 is a bad score. Algorithms for producing these estimates are outside the scope of this work, but are an active area of investigation in the field. Finally, the task of planning a free energy calculation network to rank all candidates can be converted into a weighted graph construction problem, with the minimal requirement that the resulting graph must be connected.