Randy, Can you try -ksp_type gmres and see if you still get the affect?
Barry On Mon, 25 Sep 2006, Randall Mackie wrote: > > > Barry Smith wrote: > > Randy, > > > > > Now, if I want to solve (2) above, do I simply make a call to > > > KSPSolveTranspose(ksp,b,xsol), where I've set b to the right > > > hand side of (2) > > > > Yes, this is the way we intend it to be used. You should not > > have to construct the transposed matrices. > > > > Questions: > > > > Are you using KSPSetNullSpace()? > > No > > > Are you using right or left preconditioning? Or not setting it? > > I'm not setting it, just using the default > > > > What KSP method are you using? > > What preconditioner are you using? > > -em_ksp_truemonitor \ > -em_ksp_type bcgs \ > -em_pc_type bjacobi \ > -em_sub_pc_type ilu \ > -em_sub_pc_factor_levels 3 \ > -em_sub_pc_factor_fill 6 \ > > > > > Barry > > > > > > > > On Mon, 25 Sep 2006, Randall Mackie wrote: > > > > > I have a situation where I have to solve the following problems: > > > > > > 1) Ax=b > > > > > > 2) (A)^T u = c > > > > > > A is not symmetric. > > > > > > > > > After I set up my A matrix and the preconditioner P (which is NOT the same > > > as > > > A), > > > I solve it like so: > > > > > > > > > call set_P(da,P,l,m,n,period,resist,x,y,z) > > > call set_A(da,A,l,m,n,period,resist,x,y,z) > > > > > > call MatSetBlockSize(A,3,ierr) > > > call MatSetBlockSize(P,3,ierr) > > > > > > call KSPSetOperators(ksp,A,P,DIFFERENT_NONZERO_PATTERN,ierr) > > > call KSPSetInitialGuessNonzero(ksp,PETSC_TRUE,ierr) > > > > > > call KSPSolve(ksp,b,xsol,ierr) > > > call KSPGetIterationNumber(ksp,its,ierr) > > > call KSPGetConvergedReason(ksp,reason,ierr) > > > > > > > > > Now, if I want to solve (2) above, do I simply make a call to > > > KSPSolveTranspose(ksp,b,xsol), where I've set b to the right > > > hand side of (2), or do I have to create the transposes of both > > > A and the preconditioner and just use KSPSolve? > > > > > > > > > When I've tried just using KSPSolveTranspose, the preconditioned residual > > > norm falls, but not as rapidly as when doing (1), and the true residual > > > norm > > > seems not to change much at all. > > > > > > > > > Thanks, Randy > > > > > > > > > > > > >
