Allocation of vertices to processes prior to partitioning


I have two questions related to the distribution of vertices among processes prior to calling a partitioning function.

- When using ParMETIS V3 AdaptiveRepart (), is there a performance difference between the Coupled and the Uncoupled configuration? How much?
- Let's say I'm assigning all vertices to Process 0 when using ParMETIS V3 PartKway (). Is it going to perform like the serial METIS, or is there still a benefit to using several processes?

Thank you,