On Tue, Nov 1, 2011 at 12:01, Konstantinos Kontzialis <ckontzialis at lycos.com > wrote:
> 1. I use 3.1 version of petsc. > please upgrade to 3.2 when you can > 2. I run the problem with snes_fd and pc_type lu > 3. I use a nondimensional form of the NS equations > 4. I do not specify any user defined procedure for applying the > preconditioner. I leave petsc to deal with this. > > With snes_fd I got the following results: > > Timestep 0: dt = 0.002, T = 0, Res[rho] = 1.06871e-16, Res[rhou] = > 0.00215523, Res[rhov] = 1.61374e-08, Res[E] = 6.17917e-07, CFL = 399.998 > > > /*********************Stage 1 of SSPIRK (6,4)******************/ > > 0 SNES Function norm 1.153030915909e-02 > 0 KSP preconditioned resid norm 1.153030915909e-02 true resid norm > 1.153030915909e-02 ||A||/||Ax|| 1.000000000000e+00 > 1 KSP preconditioned resid norm 1.998438714390e-11 true resid norm > 1.998438714940e-11 ||Ae||/||Ax|| 1.733204797344e-09 > > Linear solve converged due to CONVERGED_RTOL iterations 1 > 1 SNES Function norm 1.908346652619e-08 > 0 KSP preconditioned resid norm 1.908346652619e-08 true resid norm > 1.908346652619e-08 ||Ae||/||Ax|| 1.000000000000e+00 > 1 KSP preconditioned resid norm 1.407495233141e-08 true resid norm > 2.936727417791e-08 ||Ae||/||Ax|| 1.538885722759e+00 > 2 KSP preconditioned resid norm 1.983096664116e-16 true resid norm > 4.111894600521e-03 ||Ae||/||Ax|| 2.154689555421e+05 > This looks like a singular preconditioner. Suggest checking the implementation of boundary conditions. Also try -ksp_type fgmres. > My function for computing the residual of the system has the following > form: > > F(u) = Mu + R(u), > > where M is the mass matrix of the system and R(u) the residual and u is > the solution. > This does not look right. I would expect M udot = R_u(u,p) 0 = R_p(u) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111102/fe8a15bd/attachment.htm>
