Enhancing complex network controllability by minimum link direction reversal

• A method is proposed to enhance directed networks controllability by changing the direction of a small fraction of links.
• The method keeps the total number of links and topology structure unchanged.
• Candidate links are defined by one maximum matching path.
• The statistical character of candidate links provides us with an optimization strategy based on the local structure.

Controllability of complex networks has recently become one of the most popular research fields, but the importance of link direction for controllability has not been systematically considered. We propose a method to enhance controllability of a directed network by changing the direction of a small fraction of links while keeping the total number of links unchanged. The main idea of the method is to find candidate links based on the matching path. Extensive numerical simulation on many modeled networks demonstrates that this method is effective. Furthermore, we find that the nodes linked to candidate links have a distinct character, which provide us with a strategy to improve the controllability based on the local structure. Since the whole topology of many real networks is not visible and we only get some local structure information, this strategy is potentially more practical compared to those that demand complete topology information.