Thank you very much for your help and the examples provided. I was able to implement the Jacobian-times-vector (Jv) approach as recommended, and it works great!.
Art El mar, 8 jul 2025 a las 13:36, Zhang, Hong (<hongzh...@anl.gov>) escribió: > For a python example, please take a look at > src/binding/petsc4py/demo/legacy/ode/vanderpol.py and you will see how jvp > is done in the class IJacShell. > > > > Hong > > > > *From: *petsc-users <petsc-users-boun...@mcs.anl.gov> on behalf of > "Zhang, Hong via petsc-users" <petsc-users@mcs.anl.gov> > *Reply-To: *"Zhang, Hong" <hongzh...@anl.gov> > *Date: *Tuesday, July 8, 2025 at 12:21 PM > *To: *Art <mac3...@gmail.com>, "petsc-users@mcs.anl.gov" < > petsc-users@mcs.anl.gov> > *Subject: *Re: [petsc-users] Matrix-Free J*v in PETSc > > > > Hi Art, > > Here is a TS example that uses MatShell for implicit time integration and > adjoint sensitivity calculation: > src/ts/tutorials/advection-diffusion-reaction/ex5adj_mf.c > > > You will need to provide a (jvp) routine like MyIMatMult() in this > example. Adjoints require vjp (vector-Jacobian product) routines that are > also included in this example. > > Hong > > *From: *petsc-users <petsc-users-boun...@mcs.anl.gov> on behalf of Art < > mac3...@gmail.com> > *Date: *Monday, July 7, 2025 at 9:33 AM > *To: *"petsc-users@mcs.anl.gov" <petsc-users@mcs.anl.gov> > *Subject: *[petsc-users] Matrix-Free J*v in PETSc > > > > Hi all, > > I am integrating a stiff system of ODEs/PDEs using PETSc TS (typically > with BDF or other implicit time-stepping schemes), and I would like to > exploit the fact that I can efficiently compute the action of the Jacobian > on a vector (Jv) without assembling the full Jacobian matrix. Since for a > large system it becomes expensive to assemble the Jacobian in each > iteration. In scikits.odes (SUNDIALS/CVODE), there is a native API for > passing only a J*v routine to the time integrator. In my experience, when I > use only a Jacobian-vector product routine (without assembling the full > matrix), the performance improves significantly for large systems. However, > in PETSc TS, the workflow seems more matrix-centric, and I have only found > the possibility to use MatShell for the Jacobian > > Is there a way to do something similar in PETSc TS (for BDF or other > implicit schemes)? > > Currently, I use the matrix-free Newton-Krylov method to approximate the > Jacobian and have adjusted the tolerances to achieve convergence, as > recommended by Barry. In that case, I obtain similar integration times > with scikits.odes CVODE without using the Jacobian times vector. > > Best regards, > > Art >
