http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatShellSetOperation.html
Note that without an assembled matrix, you'll generally need to write your own preconditioner, which you can do using PCShell. On Fri, Nov 30, 2012 at 11:24 PM, Hesameddin Ilatikhameneh < hilatikh at purdue.edu> wrote: > Hello, > > We have a very large system (100M variables) which we want to minimize its > energy. We are using Petsc extensively for matrix operations. > I know that it is theoretically possible to use conjugate gradient method > without storing Jacobian matrix (which is very huge in this case) since the > conjugate gradient needs Jacobian times a vector not Jacobian itself. > > I read your manual about matrix free methods but I couldn't find where I > can determine that function to Jacobian times a vector. > > I appreciate your help. > > Thanks > Hesam > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20121130/a78d963d/attachment.html>
