thanx a lot! Can you write me the exact expression of the problem you're solving? Recently, I read the paper of Knoll about JFNK method (Jacobian-free NewtonKrylov methods: a survey of approaches and applications). I'm not sure whether I understood well. Please correct me. If r_0 is the first residual, J is the jacobian matrix, In the approximation J*r_0 = (F(u+\epsilon r_0)-F(u)) / \epsilon F(u) is the residual, right? But in Knoll's paper F(u) seems the right hand side. Or I am wrong.
pan --- "Vijay S. Mahadevan" <[EMAIL PROTECTED]> wrote: > I've attached the message from Ben Kirk. Also > attached is the example > program that he sent out. See below for his original > mail. > > On a side note, I have written a working code with > Matrix-free technique to > solve a nonlinear, transient diffusion-reaction > problem. It still needs few > refinements and I will send it here or maybe upload > it somewhere soon for > all those interested. > > -----Original Message----- > From: Benjamin Kirk [mailto:[EMAIL PROTECTED] > Sent: Wednesday, January 23, 2008 9:40 AM > To: Vijay M; [EMAIL PROTECTED] > Subject: Re: [Libmesh-users] Support for Matrix-free > algorithms > > Here is a really, really raw example, the comments > are not clear right now, > but I wanted to keep you informed. This requires > the latest svn branch to > work. > > Unpack it in the ./examples directory and run make. > > Run it as > > $ ./ex19-dbg -snes_view -r 4 > for a successive approximation which will converge > linearly, and > > $ ./ex19-dbg -snes_view -r 4 -snes_mf_operator > for a matrix-free approach in the iterative solver > which will converge > quadratically. > > > Anyway, I do have a question regarding using PETSc > object with LibMesh. I > > have been trying to use Petsc objects Mats, Vecs > and SNES solver with > > Libmesh but the one thing I cant seem figure out > is how to set the > > nonlinear_solver public attribute of say a > NonlinearImplicitSystem object > to > > a PETSc SNES object which I have created and > initialized separately. > Since, > > the SNES object used in the wrapper > PetscNonlinearSolver is private, I > don¹t > > understand how this can be done. > > > > Have I missed something and taken a completely > wrong path on this ? I > would > > very much appreciate any comments that you can > provide to help me out > here. > > The user interface is totally up for discussion > since I am the only one who > as exercised it to date. (I am sure Roy will have > some comments!) It seems > to me the right approach will be to add a method > which gives the user access > to the SNES object? From there the KSP, Mat, Vec, > PC, etc... can be > accessed. This would be similar to the approach > used in the > PetscLinearSolver. > > -Ben > > > -----Original Message----- > From: li pan [mailto:[EMAIL PROTECTED] > Sent: Wednesday, January 30, 2008 3:25 AM > To: [email protected] > Cc: [EMAIL PROTECTED] > Subject: matrix free scheme > > Dear all, > I remember that there was a discussion about matrix > free scheme with libmesh before X'mas. I'd like to > ask > if somebody has got a example code for this. > > thanx > > pan > > > > ____________________________________________________________________________ > ________ > Never miss a thing. Make Yahoo your home page. > http://www.yahoo.com/r/hs > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.19.16/1251 - > Release Date: 1/30/2008 > 9:29 AM > > > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.19.16/1251 - > Release Date: 1/30/2008 > 9:29 AM > > > ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
