  We propose a method for solving parity games with acyclic (DAG)
sub-structures by computing nested fixpoints of a DAG attractor function that
lives over the non-DAG parts of the game, thereby restricting the domain of the
involved fixpoint operators. Intuitively, this corresponds to accelerating
fixpoint computation by inlining cycle-free parts during the solution of parity
games, leading to earlier convergence. We also present an economic
later-appearence-record construction that takes Emerson-Lei games to parity
games, and show that it preserves DAG sub-structures; it follows that the
proposed method can be used also for the accelerated solution of Emerson-Lei
games.
