On Thu, Oct 18, 2012 at 11:07 AM, Nachiket Gokhale <gokhalen at gmail.com>wrote:
> Hi, > > I am solving a Piezoelectric problem using Petsc. The structure is > > [ K_uu K_uv ] > [K_uv ^T -K_v,v ] > > More details about the formulation: http://tinyurl.com/9hlbp4u > > K_uu has elements O(1E9) because the stiffnesses are in GPa, > K_uv has elements O(1) because piezoelectric coefficients are of that > order > K_v,v has elements O(1E-9) because the dielectric constants are of > that order. > > I am using Petsc, with pc_type LU and MUMPS for the factorization, > -ksp_type gmres. I am not sure if my solution is converging. A typical > solve seems to be doing this: > > 28 KSP preconditioned resid norm 5.642364260456e-06 true resid norm > 1.228976487745e-03 ||r(i)||/||b|| 3.317409023627e-14 > 29 KSP preconditioned resid norm 5.540718271043e-06 true resid norm > 1.228453548651e-03 ||r(i)||/||b|| 3.315997440178e-14 > 30 KSP preconditioned resid norm 1.973052106578e-03 true resid norm > 1.220399172500e-03 ||r(i)||/||b|| 3.294256047735e-14 > 31 KSP preconditioned resid norm 1.155762663956e-17 true resid norm > 2.447631111938e-04 ||r(i)||/||b|| 6.606955965570e-15 > > Is there a right way to solve this set of equations? Is PCFieldSplit > the recommended way? > First, you should really non-dimensionalize. You can see what this would give you by symmetrically scaling your problem with [ 3e4 3e-4 ], namely everything will be O(1). Second, you might get something out of using FieldSplit, but its tough to tell without knowing more about the operators. Matt > Thanks, > > -Nachiket > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20121018/099340b7/attachment.html>
