solve successive linear systems

[enjoywm at cs.wm.edu]

Hi,
I have a linear system KU=F. I need to solve it successively in several
iterations. Both K and F will be chaged in each iteration.
Q1. In each iteration I need to chage some elements in K and F. How to
allocate the space for K and F to make this changing efficiently? In
another words, to avoid copy operations.

Q2. Manual said to solve successive linear system with different
preconditioner matrix (The preconditioner matrix is same with K, so
preconditioner matrix is different as K changes) user must call
KSPSetOperators() and KSPSolve() for each solve. How to set the flag in
each solve?

Thanks!

Yixun