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
