yes, I am repeatedly calling KSPSolve. I set the operator once at the beginning, but I change some of the elements of the operator between solves without changing the nonzero pattern.
On Tue, Jan 28, 2014 at 2:58 PM, Jed Brown <[email protected]> wrote: > David Liu <[email protected]> writes: > > > Hi, I'm writing an application that solves a sparse matrix many times > using > > Pastix. I notice that the first solves takes a very long time, while the > > subsequent solves are very fast. I don't fully understand what's going on > > behind the curtains, but I'm guessing it's because the very first solve > has > > to read in the non-zero structure for the LU factorization, while the > > subsequent solves are faster because the nonzero structure doesn't > change. > > How are you doing this? Repeated calls to KSPSolve? Are you changing > the operator between solves? >
