  We present the tool Ranker for complementing B\"uchi automata (BAs). Ranker
builds on our previous optimizations of rank-based BA complementation and
pushes them even further using numerous heuristics to produce even smaller
automata. Moreover, it contains novel optimizations of specialized
constructions for complementing (i) inherently weak automata and (ii)
semi-deterministic automata, all delivered in a robust tool. The optimizations
significantly improve the usability of Ranker, as shown in an extensive
experimental evaluation with real-world benchmarks, where Ranker produced in
the majority of cases a strictly smaller complement than other state-of-the-art
tools.
