# PETSC ERROR: KSPSolve() has not converged, reason DIVERGED\_ITS

**URL:** <https://community.geodynamics.org/t/petsc-error-kspsolve-has-not-converged-reason-diverged-its/3588>\
**Category:** PyLith\
**Created:** [August 6, 2024, 2:20pm UTC](https://community.geodynamics.org/t/petsc-error-kspsolve-has-not-converged-reason-diverged-its/3588 "2024-08-06T14:20:12Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Hsiaolun](https://avatars.discourse-cdn.com/v4/letter/h/bb73d2/32.png) [@Hsiaolun](https://community.geodynamics.org/u/Hsiaolun)\
**Post date:** [August 6, 2024, 2:20pm UTC](https://community.geodynamics.org/t/petsc-error-kspsolve-has-not-converged-reason-diverged-its/3588/1 "2024-08-06T14:20:12Z")

</div>

Hello, I have a question about subduction-3d. When using the command “pylith step04\_eqcycle.cfg mat\_viscoelastic.cfg” runs pylith correctly, but when I add “–node=n” and “n \> 2”, an error occurs.

 ![Screenshot from 2024-08-06 22-18-20](https://canada1.discourse-cdn.com/flex036/uploads/geodynamics/original/2X/e/ecf03e82fb28b9ab35c0abc09b8f300248c3db93.png)

---

<div class="post-metadata">

**Author:** ![baagaard](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/baagaard/32/615_2.png) [@baagaard](https://community.geodynamics.org/u/baagaard)\
**Post date:** [August 7, 2024, 8:35pm UTC](https://community.geodynamics.org/t/petsc-error-kspsolve-has-not-converged-reason-diverged-its/3588/2 "2024-08-07T20:35:35Z")

</div>

This is a known and documented issue when running in parallel with the default preconditioner for elasticity with faults. Please refer to the boxes with warnings in the [PETSc Options](https://pylith.readthedocs.io/en/latest/user/run-pylith/petsc-options.html#solver-options) section of the manual for a discussion of the default preconditioner and when it fails in parallel.

---

<div class="post-metadata">

**Author:** ![Hsiaolun](https://avatars.discourse-cdn.com/v4/letter/h/bb73d2/32.png) [@Hsiaolun](https://community.geodynamics.org/u/Hsiaolun)\
**Post date:** [August 8, 2024, 1:27am UTC](https://community.geodynamics.org/t/petsc-error-kspsolve-has-not-converged-reason-diverged-its/3588/3 "2024-08-08T01:27:32Z")

</div>

Thank you very much for your help. I have solved the problem based on the manual. 😃