Does community algorithm suit for unconnected graph?

Hi, I have a question about the performance of community algorithm, like maxkcut, I have a graph with 3000 nodes, and 40000 rels. The contains 3 parts of data, and each part is kind of separate. When I apply community algorithm, it is very slow, run more than 3 hours and it seems never stop. I can't find the reason, not sure if it because the unconnected graph.

Does anyone has same issues?