Cycle detection in repair-based railway scheduling system

Proposes an approach for railway scheduling based on iterative repair, a technique that starts with a complete but possibly flawed schedule and searches through the space of possible repairs. The search is guided by an earliest-conflict-first heuristic that attempts to repair the earliest constraint violation while minimizing the value of objective function. Since cycles may exist among a sequence of repairs during the repair process, a cycle detection and resolution scheme is proposed to prevent infinite loops. Experimental results show that the efficiency of the repair algorithm improves significantly when cycle detection is incorporated.