Carol, I tested qcg with petsc/src/ksp/ksp/examples/tutorials/ex2.c and found it crashes with np=2, pc=bjacobi.
Then I found in http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPQCG.html Notes: This is rarely used directly Currently we allow symmetric preconditioning with the following scaling matricesPCNONE <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCNONE.html#PCNONE>: D = Identity matrix PCJACOBI <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCJACOBI.html#PCJACOBI>: D = diag [d_1, d_2, ...., d_n], where d_i = sqrt(H[i,i]) PCICC <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCICC.html#PCICC>: D = L^T, implemented with forward and backward solves. Here L is an incomplete Cholesky factor of H. Hong 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 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 >
