[petsc-users] Yet another inversion question

[Jed Brown]

On Sat, 1 May 2010 17:00:22 -0500, Barry Smith <bsmith at mcs.anl.gov> wrote:
>     This cannot be! Perhaps you used the PETSc default solver for my  
> suggestion but UMFPACK for your version? With a direct solve "all" the  
> work will be in the factorization and triangular solves so if you use  
> UMFPACK for both they both do the same amount of work.

For what it's worth, extracting a column should cost a fair amount less
than doing a solve since the factored matrix will usually have a lot
more entries.

Jed