# Issues with translating code from dolfin to dolfinx

**URL:** <https://fenicsproject.discourse.group/t/issues-with-translating-code-from-dolfin-to-dolfinx/18276>\
**Category:** dolfinx\
**Created:** [October 17, 2025, 12:19pm UTC](https://fenicsproject.discourse.group/t/issues-with-translating-code-from-dolfin-to-dolfinx/18276 "2025-10-17T12:19:38Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**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 20, 2025, 2:29pm UTC](https://fenicsproject.discourse.group/t/issues-with-translating-code-from-dolfin-to-dolfinx/18276/2 "2025-10-20T14:29:24Z")

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I don’t see any obvious errors.  
However, what is your use-case for `ident_zeros`? There might be better ways of performing the task you have in mind than modifying the PETSc matrix post assembly.

For instance: [Modify matrix diagonal -- dolfinx version for A.ident\_zeros() - #3 by dokken](https://fenicsproject.discourse.group/t/modify-matrix-diagonal-dolfinx-version-for-a-ident-zeros/9918/3)  
illustrates this.  
You might also be able to use `dolfinx.mesh.create_submesh` to restrict the function space instead.

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