[petsc-users] Errors encountered with KSPsolver with MATNEST and VECNEST

Alex Fleeter luis.saturday at gmail.com
Sat Jul 18 05:11:34 CDT 2020 

I guess using MatNest is still the most memory efficient one, am I correct?
Does MatGetLocalSubMatrix demand extra memory for generating the sub
matrices?

On Thu, Jul 16, 2020 at 4:44 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, Jul 16, 2020 at 6:54 AM Yang Juntao <Y.Juntao at hotmail.com> wrote:
>
>> Hi, Matt,
>>
>>
>>
>> In case, I want to put blocks of matrices(assembled independently)
>> together as the system matrix just as in the example. What would be your
>> recommended approach?
>>
>> I first looked into MatCreateBlockMat, but it only supports sequential
>> and then I was directed to MATNEST.  Do I have to assemble directly on
>> “system matrix”.
>>
>
> The idea is that you use
>
>
> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetLocalSubMatrix.html
>
> This does require the extra step of calling
>
>
> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSetLocalToGlobalMapping.html#MatSetLocalToGlobalMapping
>
> but you must already have this in order to get the global indices.
>
> If you use that, then you can assemble locally into AIJ or Nest with the
> same code.
>
>   Thanks,
>
>      Matt
>
>
>> “
>>
>> Matrices of this type are nominally-sparse matrices in which each "entry"
>> is a Mat
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/Mat.html#Mat>
>> object. Each Mat
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/Mat.html#Mat>
>> must have the same size and be sequential. The local and global sizes must
>> be compatible with this decomposition. For matrices containing parallel
>> submatrices and variable block sizes, see MATNEST
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MATNEST.html#MATNEST>.
>>
>>
>> “
>>
>>
>>
>> Regards
>>
>> Juntao
>>
>>
>>
>> *From:* Matthew Knepley <knepley at gmail.com>
>> *Sent:* Thursday, July 16, 2020 5:56 PM
>> *To:* Karl Yang <y.juntao at hotmail.com>
>> *Cc:* Junchao Zhang <junchao.zhang at gmail.com>; petsc-users at mcs.anl.gov
>> *Subject:* Re: [petsc-users] Errors encountered with KSPsolver with
>> MATNEST and VECNEST
>>
>>
>>
>> On Thu, Jul 16, 2020 at 5:43 AM Karl Yang <y.juntao at hotmail.com> wrote:
>>
>> Hi, Matt,
>>
>>
>>
>> Sorry for the confusion. The error shows as below without SetIS().
>>
>>
>>
>> I see the problem now. It is about the interface for MatNest.
>>
>>
>>
>> MatNest is intended _only_ as an optimization. I think you should never
>> have MatNest in user code. Here the
>>
>> problem is that MatNest only supports extraction using the ISes it was
>> created with, whereas detection is
>>
>> finding a different IS. I recommend getting everything working with AIJ,
>> and then use MatSetType() or
>>
>> -mat_type at the end to try out Nest. The interfaces are the same.
>>
>>
>>
>>   Thanks,
>>
>>
>>
>>     Matt
>>
>>
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>>
>> [0]PETSC ERROR: Arguments are incompatible
>>
>> [0]PETSC ERROR: Could not find index set
>>
>> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html
>> for trouble shooting.
>>
>> [0]PETSC ERROR: Petsc Release Version 3.12.5, Mar, 29, 2020
>>
>> [0]PETSC ERROR: ./testSolve on a arch-linux2-c-debug named ae3f0ab5a8c4
>> by Unknown Thu Jul 16 17:36:52 2020
>>
>> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++
>> --with-fc=gfortran --download-mpich --download-fblaslapack --with-cuda
>>
>> [0]PETSC ERROR: #1 MatNestFindIS() line 365 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/impls/nest/matnest.c
>>
>> [0]PETSC ERROR: #2 MatNestFindSubMat() line 425 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/impls/nest/matnest.c
>>
>> [0]PETSC ERROR: #3 MatCreateSubMatrix_Nest() line 456 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/impls/nest/matnest.c
>>
>> [0]PETSC ERROR: #4 MatCreateSubMatrix() line 7859 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/interface/matrix.c
>>
>> [0]PETSC ERROR: #5 PCSetUp_FieldSplit() line 676 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/impls/fieldsplit/fieldsplit.c
>>
>> [0]PETSC ERROR: #6 PCSetUp() line 894 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/interface/precon.c
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>>
>> [0]PETSC ERROR: Corrupt argument:
>> https://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind
>>
>> [0]PETSC ERROR: Invalid Pointer to Object: Parameter # 1
>>
>> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html
>> for trouble shooting.
>>
>> [0]PETSC ERROR: Petsc Release Version 3.12.5, Mar, 29, 2020
>>
>> [0]PETSC ERROR: ./testSolve on a arch-linux2-c-debug named ae3f0ab5a8c4
>> by Unknown Thu Jul 16 17:36:52 2020
>>
>> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++
>> --with-fc=gfortran --download-mpich --download-fblaslapack --with-cuda
>>
>> [0]PETSC ERROR: #7 MatDestroy() line 1266 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/interface/matrix.c
>>
>> [0]PETSC ERROR: #8 PCSetUp_FieldSplit() line 697 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/impls/fieldsplit/fieldsplit.c
>>
>> [0]PETSC ERROR: #9 PCSetUp() line 894 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/interface/precon.c
>>
>> [0]PETSC ERROR: #10 KSPSetUp() line 376 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itfunc.c
>>
>> KSP Object: 1 MPI processes
>>
>>   type: fgmres
>>
>>     restart=30, using Classical (unmodified) Gram-Schmidt
>> Orthogonalization with no iterative refinement
>>
>>     happy breakdown tolerance 1e-30
>>
>>   maximum iterations=10000, initial guess is zero
>>
>>   tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
>>
>>   right preconditioning
>>
>>   using UNPRECONDITIONED norm type for convergence test
>>
>> PC Object: 1 MPI processes
>>
>>   type: fieldsplit
>>
>>   PC has not been set up so information may be incomplete
>>
>>     FieldSplit with Schur preconditioner, blocksize = 1, factorization
>> FULL
>>
>>     Preconditioner for the Schur complement formed from S itself
>>
>>     Split info:
>>
>>     Split number 0 Defined by IS
>>
>>     Split number 1 Defined by IS
>>
>>     KSP solver for A00 block
>>
>>       KSP Object: (fieldsplit_0_) 1 MPI processes
>>
>>         type: preonly
>>
>>         maximum iterations=10000, initial guess is zero
>>
>>         tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
>>
>>         left preconditioning
>>
>>         using DEFAULT norm type for convergence test
>>
>>       PC Object: (fieldsplit_0_) 1 MPI processes
>>
>>         type not yet set
>>
>>         PC has not been set up so information may be incomplete
>>
>>     KSP solver for upper A00 in upper triangular factor
>>
>>         not yet available
>>
>>     KSP solver for S = A11 - A10 inv(A00) A01
>>
>>         not yet available
>>
>>   linear system matrix = precond matrix:
>>
>>   Mat Object: 1 MPI processes
>>
>>     type: nest
>>
>>     rows=15, cols=15
>>
>>       Matrix object:
>>
>>         type=nest, rows=3, cols=3
>>
>>         MatNest structure:
>>
>>         (0,0) : type=seqaij, rows=5, cols=5
>>
>>         (0,1) : NULL
>>
>>         (0,2) : type=seqaij, rows=5, cols=5
>>
>>         (1,0) : NULL
>>
>>         (1,1) : type=seqaij, rows=5, cols=5
>>
>>         (1,2) : type=seqaij, rows=5, cols=5
>>
>>         (2,0) : type=seqaij, rows=5, cols=5
>>
>>         (2,1) : type=seqaij, rows=5, cols=5
>>
>>         (2,2) : NULL
>>
>> Segmentation fault (core dumped)
>>
>>
>>
>> Attached is the test code.
>>
>>
>>
>> Regards
>>
>> JT
>>
>>
>>
>>
>> On Jul 16 2020, at 5:30 pm, Matthew Knepley <knepley at gmail.com> wrote:
>>
>> On Thu, Jul 16, 2020 at 1:23 AM Karl Yang <y.juntao at hotmail.com
>> <https://link.getmailspring.com/link/1D2D2990-B215-4510-B196-F29BD06D4684@getmailspring.com/0?redirect=mailto%3Ay.juntao%40hotmail.com&recipient=a25lcGxleUBnbWFpbC5jb20%3D>>
>> wrote:
>>
>> [image: Sent from Mailspring]
>>
>> Hi, Junchao,
>>
>>
>>
>> Thank you. It works. :)
>>
>>
>>
>> May I ask some follow up question regarding the same example about
>> fieldsplit. I am trying to learn about matnest with fieldsplit
>> preconditioner on manual page 94. But I get a bit lost trying to understand
>> fields, ISs once it is not eactly the same on the manual.
>>
>>
>>
>> In this same example, I tried to use PCFIELDSPLIT and
>> PCFieldSplitSetDetectSaddlePoint as follows.
>>
>>
>>
>> You cannot mix DetectSaddlePoint() with SetIS() since the detection tries
>> to make the proper ISes. Maybe we should check that.
>>
>>
>>
>>   Thanks,
>>
>>
>>
>>      Matt
>>
>>
>>
>> IS rows[3];
>>
>> IS cols[3];
>>
>> MatNestGetISs(testMesh->system, rows, cols);
>>
>>
>>
>> KSP ksp;
>>
>> PC  pc;
>>
>> KSPCreate(PETSC_COMM_WORLD, &ksp);
>>
>> KSPSetType(ksp, KSPFGMRES);
>>
>> KSPSetOperators(ksp, testMesh->system, testMesh->system);
>>
>> KSPGetPC(ksp, &pc);
>>
>> PCFieldSplitSetIS(pc, "u", rows[0]);
>>
>> PCFieldSplitSetIS(pc, "v", rows[1]);
>>
>> PCFieldSplitSetIS(pc, "p", rows[2]);
>>
>> PCSetType(pc, PCFIELDSPLIT);
>>
>> PCFieldSplitSetDetectSaddlePoint(pc, PETSC_TRUE);
>>
>> KSPSetUp(ksp);
>>
>> KSPSolve(ksp, testMesh->rhs, testMesh->solution);
>>
>>
>>
>> But I will get the following error,
>>
>>
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>>
>> [0]PETSC ERROR: Arguments are incompatible
>>
>> [0]PETSC ERROR: Could not find index set
>>
>> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html for
>> trouble shooting.
>>
>> [0]PETSC ERROR: Petsc Release Version 3.12.5, Mar, 29, 2020
>>
>> [0]PETSC ERROR: ./testSolve on a arch-linux2-c-debug named f601294ac804
>> by Unknown Thu Jul 16 13:08:39 2020
>>
>> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++
>> --with-fc=gfortran --download-mpich --download-fblaslapack --with-cuda
>>
>> [0]PETSC ERROR: #1 MatNestFindIS() line 365 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/impls/nest/matnest.c
>>
>> [0]PETSC ERROR: #2 MatNestFindSubMat() line 425 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/impls/nest/matnest.c
>>
>> [0]PETSC ERROR: #3 MatCreateSubMatrix_Nest() line 456 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/impls/nest/matnest.c
>>
>> [0]PETSC ERROR: #4 MatCreateSubMatrix() line 7859 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/interface/matrix.c
>>
>> [0]PETSC ERROR: #5 PCSetUp_FieldSplit() line 676 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/impls/fieldsplit/fieldsplit.c
>>
>> [0]PETSC ERROR: #6 PCSetUp() line 894 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/interface/precon.c
>>
>> [0]PETSC ERROR: #7 KSPSetUp() line 376 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itfunc.c
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>>
>> [0]PETSC ERROR: Corrupt argument:
>> https://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind
>>
>> [0]PETSC ERROR: Invalid Pointer to Object: Parameter # 1
>>
>> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html for
>> trouble shooting.
>>
>> [0]PETSC ERROR: Petsc Release Version 3.12.5, Mar, 29, 2020
>>
>> [0]PETSC ERROR: ./testSolve on a arch-linux2-c-debug named f601294ac804
>> by Unknown Thu Jul 16 13:08:39 2020
>>
>> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++
>> --with-fc=gfortran --download-mpich --download-fblaslapack --with-cuda
>>
>> [0]PETSC ERROR: #8 MatDestroy() line 1266 in
>> /usr/local/petsc/petsc-3.12.5/src/mat/interface/matrix.c
>>
>> [0]PETSC ERROR: #9 PCSetUp_FieldSplit() line 697 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/impls/fieldsplit/fieldsplit.c
>>
>> [0]PETSC ERROR: #10 PCSetUp() line 894 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/interface/precon.c
>>
>> [0]PETSC ERROR: #11 KSPSetUp() line 376 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itfunc.c
>>
>> [0]PETSC ERROR: #12 KSPSolve() line 703 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itfunc.c
>>
>>
>>
>> I read about the examples on the manual and mostly are based on 2*2
>> blocks but still cannot figure out how pcfieldsplit should be set in this 3*
>>  **3 blocks, and how IS should be set accordingly. I read about
>> -fieldsplit_1_pc_type none option suggested on the documentation, but I am
>> not sure is it still valid in a 33 blocks.*
>>
>>
>>
>> *Regards*
>>
>> *JT*
>>
>> On Jul 16 2020, at 6:57 am, Junchao Zhang <junchao.zhang at gmail.com>
>> wrote:
>>
>> Adding the MatNestSetVecType() line fixed the problem.  But I don't know
>> why petsc had this weird design originally.
>>
>>
>>
>>       MatCreateNest(PETSC_COMM_WORLD, 3, NULL, 3, NULL, mblock,
>> &testMesh->system);
>>
>>  +   MatNestSetVecType(testMesh->system,VECNEST);
>>
>>
>>
>> --Junchao Zhang
>>
>>
>>
>>
>>
>> On Wed, Jul 15, 2020 at 2:16 PM Karl Yang <y.juntao at hotmail.com> wrote:
>>
>> Hi, Barry,
>>
>>
>>
>> I created a minimum example to reproduce the error. The example code is
>> attached.
>>
>>
>>
>> Mat Object: 1 MPI processes
>>
>>   type: nest
>>
>>   Matrix object:
>>
>>     type=nest, rows=3, cols=3
>>
>>     MatNest structure:
>>
>>     (0,0) : type=seqaij, rows=5, cols=5
>>
>>     (0,1) : NULL
>>
>>     (0,2) : type=seqaij, rows=5, cols=5
>>
>>     (1,0) : NULL
>>
>>     (1,1) : type=seqaij, rows=5, cols=5
>>
>>     (1,2) : type=seqaij, rows=5, cols=5
>>
>>     (2,0) : type=seqaij, rows=5, cols=5
>>
>>     (2,1) : type=seqaij, rows=5, cols=5
>>
>>     (2,2) : NULL
>>
>> Vec Object: 1 MPI processes
>>
>>   type: nest
>>
>>   VecNest, rows=3,  structure:
>>
>>   (0) : type=seq, rows=5
>>
>>     Vec Object: 1 MPI processes
>>
>>       type: seq
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>   (1) : type=seq, rows=5
>>
>>     Vec Object: 1 MPI processes
>>
>>       type: seq
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>   (2) : type=seq, rows=5
>>
>>     Vec Object: 1 MPI processes
>>
>>       type: seq
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>>     1.
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>>
>> [0]PETSC ERROR: Invalid argument
>>
>> [0]PETSC ERROR: Nest vector argument 2 not setup.
>>
>> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html for
>> trouble shooting.
>>
>> [0]PETSC ERROR: Petsc Release Version 3.12.5, Mar, 29, 2020
>>
>> [0]PETSC ERROR: ./testSolve on a arch-linux2-c-debug named f601294ac804
>> by Unknown Thu Jul 16 03:11:02 2020
>>
>> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++
>> --with-fc=gfortran --download-mpich --download-fblaslapack --with-cuda
>>
>> [0]PETSC ERROR: #1 VecCopy_Nest() line 68 in
>> /usr/local/petsc/petsc-3.12.5/src/vec/vec/impls/nest/vecnest.c
>>
>> [0]PETSC ERROR: #2 VecCopy() line 1577 in
>> /usr/local/petsc/petsc-3.12.5/src/vec/vec/interface/vector.c
>>
>> [0]PETSC ERROR: #3 KSPInitialResidual() line 61 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itres.c
>>
>> [0]PETSC ERROR: #4 KSPSolve_GMRES() line 236 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/impls/gmres/gmres.c
>>
>> [0]PETSC ERROR: #5 KSPSolve() line 760 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itfunc.c
>>
>> On Jul 16 2020, at 2:39 am, Barry Smith <bsmith at petsc.dev> wrote:
>>
>>
>>
>>   Could be a bug in PETSc, please send a sample program that produces the
>> problem.
>>
>>
>>
>>   Barry
>>
>>
>>
>>
>>
>> On Jul 15, 2020, at 1:28 PM, Karl Yang <y.juntao at hotmail.com
>> <https://link.getmailspring.com/link/060AB2C3-F3D7-408C-99CF-C4D1B27DD59F@getmailspring.com/0?redirect=mailto%3Ay.juntao%40hotmail.com&recipient=cGV0c2MtdXNlcnNAbWNzLmFubC5nb3Y%3D>>
>> wrote:
>>
>>
>>
>> Hi, Barry,
>>
>>
>>
>> Thanks for your reply. I output the matrix and vec with matview and
>> vecview. And I think I do have the values set as it has been shown.
>>
>>
>>
>> Mat Object: 1 MPI processes
>>
>>   type: nest
>>
>>   Matrix object:
>>
>>     type=nest, rows=3, cols=3
>>
>>     MatNest structure:
>>
>>     (0,0) : type=seqaij, rows=25, cols=25
>>
>>     (0,1) : NULL
>>
>>     (0,2) : type=seqaij, rows=25, cols=25
>>
>>     (1,0) : NULL
>>
>>     (1,1) : type=seqaij, rows=25, cols=25
>>
>>     (1,2) : type=seqaij, rows=25, cols=25
>>
>>     (2,0) : type=seqaij, rows=25, cols=25
>>
>>     (2,1) : type=seqaij, rows=25, cols=25
>>
>>     (2,2) : NULL
>>
>> Vec Object: 1 MPI processes
>>
>>   type: nest
>>
>>   VecNest, rows=3,  structure:
>>
>>   (0) : type=seq, rows=25
>>
>>     Vec Object: 1 MPI processes
>>
>>       type: seq
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     75.8279
>>
>>     -51.0776
>>
>>     -75.8279
>>
>>     0.
>>
>>     0.
>>
>>     -90.8404
>>
>>     58.7011
>>
>>     90.8404
>>
>>     0.
>>
>>     0.
>>
>>     -75.8279
>>
>>     51.0776
>>
>>     75.8279
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>   (1) : name="Vec_0x84000000_0", type=seq, rows=25
>>
>>     Vec Object: Vec_0x84000000_0 1 MPI processes
>>
>>       type: seq
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     75.8279
>>
>>     -51.0776
>>
>>     -75.8279
>>
>>     0.
>>
>>     0.
>>
>>     -90.8404
>>
>>     58.7011
>>
>>     90.8404
>>
>>     0.
>>
>>     0.
>>
>>     -75.8279
>>
>>     51.0776
>>
>>     75.8279
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>   (2) : type=seq, rows=25
>>
>>     Vec Object: 1 MPI processes
>>
>>       type: seq
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>>     0.
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>>
>> [0]PETSC ERROR: Invalid argument
>>
>> [0]PETSC ERROR: Nest vector argument 4 not setup.
>>
>> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html
>> <https://link.getmailspring.com/link/060AB2C3-F3D7-408C-99CF-C4D1B27DD59F@getmailspring.com/1?redirect=https%3A%2F%2Fwww.mcs.anl.gov%2Fpetsc%2Fdocumentation%2Ffaq.html&recipient=cGV0c2MtdXNlcnNAbWNzLmFubC5nb3Y%3D> for
>> trouble shooting.
>>
>> [0]PETSC ERROR: Petsc Release Version 3.12.5, Mar, 29, 2020
>>
>> [0]PETSC ERROR: ./testSolve on a arch-linux2-c-debug named f601294ac804
>> by Unknown Thu Jul 16 02:15:26 2020
>>
>> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++
>> --with-fc=gfortran --download-mpich --download-fblaslapack --with-cuda
>>
>> [0]PETSC ERROR: #1 VecPointwiseMult_Nest() line 245 in
>> /usr/local/petsc/petsc-3.12.5/src/vec/vec/impls/nest/vecnest.c
>>
>> [0]PETSC ERROR: #2 VecPointwiseMult() line 1107 in
>> /usr/local/petsc/petsc-3.12.5/src/vec/vec/interface/vector.c
>>
>> [0]PETSC ERROR: #3 PCApply_Jacobi() line 272 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/impls/jacobi/jacobi.c
>>
>> [0]PETSC ERROR: #4 PCApply() line 444 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/pc/interface/precon.c
>>
>> [0]PETSC ERROR: #5 KSP_PCApply() line 281 in
>> /usr/local/petsc/petsc-3.12.5/include/petsc/private/kspimpl.h
>>
>> [0]PETSC ERROR: #6 KSPInitialResidual() line 65 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itres.c
>>
>> [0]PETSC ERROR: #7 KSPSolve_GMRES() line 236 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/impls/gmres/gmres.c
>>
>> [0]PETSC ERROR: #8 KSPSolve() line 760 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itfunc.c
>>
>>
>>
>> On Jul 16 2020, at 2:13 am, Barry Smith <bsmith at petsc.dev
>> <https://link.getmailspring.com/link/060AB2C3-F3D7-408C-99CF-C4D1B27DD59F@getmailspring.com/2?redirect=mailto%3Absmith%40petsc.dev&recipient=cGV0c2MtdXNlcnNAbWNzLmFubC5nb3Y%3D>>
>> wrote:
>>
>>
>>
>>   From the error message the second vector you are using to form the nest
>> vector has not been completely created/set up. Make sure you called either
>> VecCreateSeq(), VecCreateMPI() or did VecCreate(), VecSetType(), VecSetUp()
>> and if it is the right hand side make sure you put numerical values in it.
>>
>>
>>
>>    Barry
>>
>>
>>
>>
>>
>> On Jul 15, 2020, at 1:05 PM, Karl Yang <y.juntao at hotmail.com
>> <https://link.getmailspring.com/link/060AB2C3-F3D7-408C-99CF-C4D1B27DD59F@getmailspring.com/3?redirect=https%3A%2F%2Flink.getmailspring.com%2Flink%2F540F752A-DB59-4878-9C98-B8F4B4D9FD0D%40getmailspring.com%2F0%3Fredirect%3Dmailto%253Ay.juntao%2540hotmail.com%26recipient%3DYnNtaXRoQHBldHNjLmRldg%253D%253D&recipient=cGV0c2MtdXNlcnNAbWNzLmFubC5nb3Y%3D>>
>> wrote:
>>
>>
>>
>> Hello,
>>
>>
>>
>> I'm trying to solve a 2*2 block matrix system.
>>
>> I managed to form a 2*2 MatNest and a 21 VecNest. However when I try to
>> make use of ksp solve, I encounter the following error. There is only one
>> or two examples on MatNest and VecNest. I could not figure out what could
>> be the trouble.
>>
>>
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>>
>> [0]PETSC ERROR: Invalid argument
>>
>> [0]PETSC ERROR: Nest vector argument 2 not setup.
>>
>> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html
>> <https://link.getmailspring.com/link/060AB2C3-F3D7-408C-99CF-C4D1B27DD59F@getmailspring.com/4?redirect=https%3A%2F%2Flink.getmailspring.com%2Flink%2F540F752A-DB59-4878-9C98-B8F4B4D9FD0D%40getmailspring.com%2F1%3Fredirect%3Dhttps%253A%252F%252Fwww.mcs.anl.gov%252Fpetsc%252Fdocumentation%252Ffaq.html%26recipient%3DYnNtaXRoQHBldHNjLmRldg%253D%253D&recipient=cGV0c2MtdXNlcnNAbWNzLmFubC5nb3Y%3D> for
>> trouble shooting.
>>
>> [0]PETSC ERROR: Petsc Release Version 3.12.5, Mar, 29, 2020
>>
>> [0]PETSC ERROR: ./testSolve on a arch-linux2-c-debug named f601294ac804
>> by Unknown Thu Jul 16 01:56:11 2020
>>
>> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++
>> --with-fc=gfortran --download-mpich --download-fblaslapack --with-cuda
>>
>> [0]PETSC ERROR: #1 VecCopy_Nest() line 68 in
>> /usr/local/petsc/petsc-3.12.5/src/vec/vec/impls/nest/vecnest.c
>>
>> [0]PETSC ERROR: #2 VecCopy() line 1577 in
>> /usr/local/petsc/petsc-3.12.5/src/vec/vec/interface/vector.c
>>
>> [0]PETSC ERROR: #3 KSPInitialResidual() line 61 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itres.c
>>
>> [0]PETSC ERROR: #4 KSPSolve_GMRES() line 236 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/impls/gmres/gmres.c
>>
>> [0]PETSC ERROR: #5 KSPSolve() line 760 in
>> /usr/local/petsc/petsc-3.12.5/src/ksp/ksp/interface/itfunc.c
>>
>>
>>
>> Regards
>>
>> JT
>>
>>
>>
>>
>>
>> --
>>
>> 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
>>
>>
>>
>> https://www.cse.buffalo.edu/~knepley/
>> <https://link.getmailspring.com/link/1D2D2990-B215-4510-B196-F29BD06D4684@getmailspring.com/1?redirect=http%3A%2F%2Fwww.cse.buffalo.edu%2F~knepley%2F&recipient=a25lcGxleUBnbWFpbC5jb20%3D>
>>
>>
>>
>>
>> --
>>
>> 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
>>
>>
>>
>> https://www.cse.buffalo.edu/~knepley/
>> <http://www.cse.buffalo.edu/~knepley/>
>>
>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
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