Direct Linear Solvers

[Julian]

Hello,

I looked at the linear solvers summary page and I could find three direct
solvers that do not use any external packages. But I could find an example
for only one of them (LU). The link to the cholesky solver does not have any
example file. I am new to PETSc and I don't fully understand how the
different solvers are invoked. Do I just change  PCSetType(pc,PCLU); to  
PCSetType(pc,PCCHOLESKY); ?

And the "XXt and Xyt" solver does not have any link. How do I use that
solver?

Also, do the direct solvers do its own internal renumbering to reduce the
matrix bandwidth? Or do we have to take care of that outside of PETSc?

Thanks,
Julian.