protected void completeSubRound() {
        this.previousMap = new ConcurrentHashMap<>(this.currentMap);
        this.inExecute = !this.inExecute;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/process/computer/TinkerMemory.java