[Dune] Alu3dgridfactory

[Guo Hua]

Dear Dune Developers

Sorry for asking too many getting started questions yesterday.
I will be more careful before asking questions.

Here is a question that Benedikt also suggested to ask when using
the alugridfactory to generate the parallel grid.

I am a little confused of how to use it? Suppose we have 10 elements, and 2 processors.
while processor 0 gets elements 0-4 as interior type, and processor 1 gets elements 5-9 as interior type.

1, on processor 0, insert elements 0-4; on processor 1, insert elements 5-9.
2, only on master processor, I insert all 10 elements, and then using loadbalance() function.
3, on both processors, I insert all 10 elements, and then using loadbalance() function.

I wonder which strategy is correct?

Cheers
Hua