PETSc implementation of qcg only allows symmetric preconditioner, which is set in the code. Hong
On Mon, Jun 29, 2015 at 9:54 AM, Matthew Knepley <[email protected]> wrote: > On Mon, Jun 29, 2015 at 9:22 AM, <[email protected]> wrote: > >> All, >> >> I am trying to use KSPSolve for a QCG solver using petsc 3.4.3 and it >> gives me the error of "PC does not have left symmetric apply!". Further >> reading on the web pages suggest I > > > CG is the Krylov Solver (KSP), but the error message is about the > Preconditioner (PC). QCG by default uses symmetric application, and by > default the PC is ILU which does not have a symmetric apply. You can use > -ksp_pc_side left > > Thanks, > > Matt > > >> need to use KSPSetPCSide to set up a symmetric side for the solver. >> However, this does not seem to work. I am doing the following in an F90 >> code: >> >> call KSPSetPCType(ksp_ptr%ksp, 'qcg', petsc_err) >> call KSPSetPCSide(ksp_ptr%ksp, PC_SYMMETRIC, petsc_err) >> >> but I still get the same failure message when I call >> KSPSolve(ksp_ptr%ksp..) later on. >> >> Any ideas as to why this is not working? >> >> Carol >> >> >> >> >> >> Dr Carol Brickley >> BSc,PhD,ARCS,DIC,MBCS >> >> Senior Software Engineer >> Applied Computer Science >> DS+T, >> AWE >> Aldermaston >> Reading >> Berkshire >> RG7 4PR >> >> Direct: 0118 9855035 >> >> >> >> ___________________________________________________ >> ____________________________ >> >> The information in this email and in any attachment(s) is >> commercial in confidence. If you are not the named addressee(s) >> or >> if you receive this email in error then any distribution, copying or >> use of this communication or the information in it is strictly >> prohibited. Please notify us immediately by email at >> admin.internet(at)awe.co.uk, and then delete this message from >> your computer. While attachments are virus checked, AWE plc >> does not accept any liability in respect of any virus which is not >> detected. >> >> AWE Plc >> Registered in England and Wales >> Registration No 02763902 >> AWE, Aldermaston, Reading, RG7 4PR >> > > > > -- > 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 >
