[petsc-users] TSTHETA not working without explicit declaration with TSSetRHSJacobian

[Ali Berk Kahraman]

My apologies for missing this earlier, but I have found these lines in 
the documentation that provides the solution for my problem.

"To use a fully implicit method like TSTHETA or TSGL, either provide the 
Jacobian of F () (and G()
if G() is provided) or use a DM that provides a coloring so the Jacobian 
can be computed efficiently
via finite differences."

However, I'm still confused with this, since the computation process of 
the Jacobian happens anyway, instead of giving an error such as "no 
jacobian is entered, aborting".


On 12-10-2017 19:45, Ali Berk Kahraman wrote:
> Hello All,
>
>
> I am trying to use TS solver without declaring RHS Jacobian, because I 
> do not have it analytically. I'm getting the error posted at the end 
> of the e-mail. As I understand, the SNES solver within the TS solver 
> sees that I have not declared a Jacobian, so it calls the function 
> SNESComputeJacobianColor to get a finite difference aproximation of 
> the Jacobian, as I am too lazy to make this approximation myself, and 
> SNESComputeJacobianColor calls MatFDColoringCreate() and this function 
> finally gives the error "Matrix is in wrong state, Matrix must be 
> assembled by calls to MatAssemblyBegin/End(); ".
>
> I am not sure if this is a bug, or it is something I'm doing wrong. It 
> looks like a bug to me since the error is generated when the code 
> understands that I haven't provided a Jacobian and consequently trying 
> to compute it for me. However, I cannot be sure because I'm still 
> pretty inexperienced using PETSc, so I'm writing this here and not to 
> petsc-maint. Any ideas?
>
>
> Best Regards ,
>
> Ali
>
>
> [0]PETSC ERROR: --------------------- Error Message 
> --------------------------------------------------------------
> [0]PETSC ERROR: Object is in wrong state
> [0]PETSC ERROR: Matrix must be assembled by calls to 
> MatAssemblyBegin/End();
> [0]PETSC ERROR: See 
> http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.8.0, unknown
> [0]PETSC ERROR: ./FastWavelet1DTransientHeat on a arch-linux2-c-debug 
> named abk-CFDLab by abk Thu Oct 12 19:39:21 2017
> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++ 
> --with-fc=gfortran --download-mpich --download-fblaslapack
> [0]PETSC ERROR: #1 MatFDColoringCreate() line 464 in 
> /home/abk/petsc/src/mat/matfd/fdmatrix.c
> [0]PETSC ERROR: #2 SNESComputeJacobianDefaultColor() line 83 in 
> /home/abk/petsc/src/snes/interface/snesj2.c
> [0]PETSC ERROR: #3 SNESComputeJacobian() line 2358 in 
> /home/abk/petsc/src/snes/interface/snes.c
> [0]PETSC ERROR: #4 SNESSolve_KSPONLY() line 36 in 
> /home/abk/petsc/src/snes/impls/ksponly/ksponly.c
> [0]PETSC ERROR: #5 SNESSolve() line 4106 in 
> /home/abk/petsc/src/snes/interface/snes.c
> [0]PETSC ERROR: #6 TS_SNESSolve() line 176 in 
> /home/abk/petsc/src/ts/impls/implicit/theta/theta.c
> [0]PETSC ERROR: #7 TSStep_Theta() line 216 in 
> /home/abk/petsc/src/ts/impls/implicit/theta/theta.c
> [0]PETSC ERROR: #8 TSStep() line 4120 in 
> /home/abk/petsc/src/ts/interface/ts.c
> [0]PETSC ERROR: #9 TSSolve() line 4374 in 
> /home/abk/petsc/src/ts/interface/ts.c
> [0]PETSC ERROR: #10 main() line 886 in 
> /home/abk/Dropbox/MyWorkspace/WaveletCollocation/FastWaveletCollocation1D/FastWavelet1DTransientHeat.c
> [0]PETSC ERROR: No PETSc Option Table entries
> [0]PETSC ERROR: ----------------End of Error Message -------send 
> entire error message to petsc-maint at mcs.anl.gov----------
> application called MPI_Abort(MPI_COMM_WORLD, 73) - process 0
> [unset]: aborting job:
> application called MPI_Abort(MPI_COMM_WORLD, 73) - process 0
>
>
> ------------------
> (program exited with code: 73)
> Press return to continue
>
>