Hello,
I want to solve a linear system with conjugate gradient and multigrid
preconditioner. I am using petsc4py. The solution is a Vector of type NEST and
the operator is a matrix-free operator created using PETSc.Mat().createPython.
The restriction and interpolation operators are all type NEST and their VecType
is set to NEST. As smoother I am using CG without preconditioner. For the
moment I am just using a classical V-cycle with 2 levels.
I am able to solve the system with CG without the MG preconditioner. However,
when I try to solve it with the MG preconditioner, it throws this error:
Traceback (most recent call last):
File "/home/elena-hp/code/Poisson_MG_Petsc.py", line 321, in <module>
solver.solve(b, u)
File "petsc4py/PETSc/KSP.pyx", line 1782, in petsc4py.PETSc.KSP.solve
petsc4py.PETSc.Error: error code 62
[0] KSPSolve() at /home/elena-hp/petsc/src/ksp/ksp/interface/itfunc.c:1089
[0] KSPSolve_Private() at
/home/elena-hp/petsc/src/ksp/ksp/interface/itfunc.c:912
[0] KSPSolve_CG() at /home/elena-hp/petsc/src/ksp/ksp/impls/cg/cg.c:213
[0] KSP_PCApply() at /home/elena-hp/petsc/include/petsc/private/kspimpl.h:414
[0] PCApply() at /home/elena-hp/petsc/src/ksp/pc/interface/precon.c:528
[0] PCApply_MG() at /home/elena-hp/petsc/src/ksp/pc/impls/mg/mg.c:651
[0] PCApply_MG_Internal() at /home/elena-hp/petsc/src/ksp/pc/impls/mg/mg.c:629
[0] PCMGMCycle_Private() at /home/elena-hp/petsc/src/ksp/pc/impls/mg/mg.c:27
[0] KSPSolve() at /home/elena-hp/petsc/src/ksp/ksp/interface/itfunc.c:1089
[0] KSPSolve_Private() at
/home/elena-hp/petsc/src/ksp/ksp/interface/itfunc.c:912
[0] KSPSolve_CG() at /home/elena-hp/petsc/src/ksp/ksp/impls/cg/cg.c:162
[0] VecCopy() at /home/elena-hp/petsc/src/vec/vec/interface/vector.c:1796
[0] VecCopyAsync_Private() at
/home/elena-hp/petsc/src/vec/vec/interface/vector.c:1755
[0] VecCopy_Nest() at /home/elena-hp/petsc/src/vec/vec/impls/nest/vecnest.c:56
[0] Invalid argument
[0] Nest vector argument 2 not setup.
The error does not appear when the operator is also of type NEST and the
VecType is set to NEST. Unfortunately, for my application I cannot write the
operator as type NEST.
I think that the problem is related to the fact that the method createVecs() of
the matrix-free operator does not return NEST vectors. I tried to do
setVecType(PETSc.Vec.Type.NEST) on the matrix-free operator but when I call
createVecs() it throws this error:
Traceback (most recent call last):
File "petsc4py/PETSc/libpetsc4py.pyx", line 965, in
petsc4py.PETSc.MatCreateVecs_Python
petsc4py.PETSc.Error: error code 86
[0] MatCreateVecs() at /home/elena-hp/petsc/src/mat/interface/matrix.c:9557
[0] VecSetType() at /home/elena-hp/petsc/src/vec/vec/interface/vecreg.c:140
[0] Unknown type. Check for miss-spelling or missing package:
https://urldefense.us/v3/__https://petsc.org/release/install/install/*external-packages__;Iw!!G_uCfscf7eWS!dEBOuSXxIqEDpI33Xza0TlRPC5n6sN3fXNslohXzfITEmMwZLwQWJUTyNE-mMJHiXZjxQ-OlWu5625crKTR81qTlPMyhvkR09mUB$
[0] Unknown vector type: nest
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "petsc4py/PETSc/Mat.pyx", line 3411, in petsc4py.PETSc.Mat.createVecs
petsc4py.PETSc.Error: error code 101
[0] MatCreateVecs() at /home/elena-hp/petsc/src/mat/interface/matrix.c:9552
Do you know how to fix this?
Thank you in advance.
Regards,
Elena
