# PETSc Krylov Solver RuntimeError with fine mesh

**URL:** <https://fenicsproject.discourse.group/t/petsc-krylov-solver-runtimeerror-with-fine-mesh/3418>\
**Category:** I/O\
**Created:** [June 3, 2020, 10:27am UTC](https://fenicsproject.discourse.group/t/petsc-krylov-solver-runtimeerror-with-fine-mesh/3418 "2020-06-03T10:27:59Z")\
**Posts on this page:** 2\
**Page:** 2

<div class="post-metadata">

**Author:** ![Notting\_X](https://avatars.discourse-cdn.com/v4/letter/n/91b2a8/32.png) [@Notting\_X](https://fenicsproject.discourse.group/u/Notting_X)\
**Post date:** [October 28, 2022, 2:48pm UTC](https://fenicsproject.discourse.group/t/petsc-krylov-solver-runtimeerror-with-fine-mesh/3418/22 "2022-10-28T14:48:03Z")

</div>

the dolfinx is the newest fenics project,but the version of fenics is v2019.1.0 on my machine.  
How should this be resolved in this version？

---

<div class="post-metadata">

**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [October 28, 2022, 3:08pm UTC](https://fenicsproject.discourse.group/t/petsc-krylov-solver-runtimeerror-with-fine-mesh/3418/23 "2022-10-28T15:08:04Z")

</div>

You would need to bring your CFL number down.

For instance using an implicit scheme helps.  
Also reducing the time step size helps. See [Courant–Friedrichs–Lewy condition - Wikipedia](https://en.m.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition)

[Previous page](https://fenicsproject.discourse.group/t/petsc-krylov-solver-runtimeerror-with-fine-mesh/3418.md?page=1)