# Unable to solve linear system using PETSc Krylov solver. PETSc reason DIVERGED_NANORINF

Hello, everyone. I have a question, during my study I have a problem like this

``````
Assembling the weak form of operator 'Op1'...
Collecting data for assembler construction...
Data collection finished.
Precalculating singular integrals...
Precalculation of singular integrals took 12.1156 s
Assembly of the weak form of operator 'Op1' took 39.6848 s
Assembling the weak form of operator 'Op2'...
Collecting data for assembler construction...
Data collection finished.
Assembly of the weak form of operator 'Op2' took 0.0617588 s
Calculating the (pseudo)inverse of operator 'Op2'...
Calculation of the (pseudo)inverse of operator 'Op2' took 0.0851854 s
Solving linear system of size 39585 x 39585 (PETSc Krylov solver).
Traceback (most recent call last):
File "newtry.py", line 52, in <module>
for i in range (300): llg.step(state, 2e-11)
File "/usr/local/lib/python2.7/dist-packages/magnumfe/integrators/llg_alouges_project.py", line 151, in step
File "/usr/local/lib/python2.7/dist-packages/magnumfe/integrators/llg_alouges_project.py", line 148, in step
File "/usr/local/lib/python2.7/dist-packages/magnumfe/integrators/llg_alouges_project.py", line 134, in calculate_v
File "/usr/local/lib/python2.7/dist-packages/magnumfe/integrators/llg_alouges_project.py", line 132, in calculate_v
File "/usr/local/lib/python2.7/dist-packages/magnumfe/integrators/llg_alouges_project.py", line 132, in calculate_v
File "/usr/lib/python2.7/dist-packages/dolfin/fem/solving.py", line 279, in solve
return cpp.la_solve(*args)
File "/usr/lib/python2.7/dist-packages/dolfin/cpp/la.py", line 4279, in la_solve
return _la.la_solve(*args)
RuntimeError:

*** -------------------------------------------------------------------------
*** DOLFIN encountered an error. If you are not able to resolve this issue
*** using the information listed below, you can ask for help at
***
***     fenics@fenicsproject.org
***
*** Remember to include the error message listed below and, if possible,
*** include a *minimal* running example to reproduce the error.
***
*** -------------------------------------------------------------------------
*** Error:   Unable to solve linear system using PETSc Krylov solver.
*** Reason:  Solution failed to converge in 0 iterations (PETSc reason DIVERGED_NANORINF, residual norm ||r|| = -nan).
*** Where:   This error was encountered inside PETScKrylovSolver.cpp.
*** Process: unknown
***
*** DOLFIN version: 1.5.0
*** Git changeset:  unknown
*** -------------------------
``````

[Mesh file (created by Salome), XML and XDMF files and PYTHON code which you can check and try] (https://drive.google.com/drive/folders/1ZhAbf1Npsx0ljIlncKzJ_U6ChZUyrPwN?usp=drive_link)
Could you explain me why it cannot solve linear system and how I can fix it? Thanks in advance.

Please double check the permissions of the google drive link: when I click on it, I get redirected to the login page, as if the file was not public.

Furthermore, is there a specific reason why you need to use FEniCS 1.5.0? Itâ€™s going to be very hard for anyone to run your code, considering that it FEniCS 1.5.0 is dated 2015 and uses python2, which most modern systems do not ship anymore.

Unfortunately, I have to use this version of Dolfin which creates a lot of the obstacles, which I know sometimes solved in next version of Dolfin. P.S. I check GoogleDrive again.