# SNES Function norm meaning

**URL:** <https://community.freefem.org/t/snes-function-norm-meaning/4001>\
**Category:** General Discussion\
**Created:** [July 11, 2025, 7:27am UTC](https://community.freefem.org/t/snes-function-norm-meaning/4001 "2025-07-11T07:27:18Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ipnglt](https://avatars.discourse-cdn.com/v4/letter/i/71e660/32.png) [@ipnglt](https://community.freefem.org/u/ipnglt)\
**Post date:** [July 11, 2025, 7:27am UTC](https://community.freefem.org/t/snes-function-norm-meaning/4001/1 "2025-07-11T07:27:18Z")

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Dear all,

I am using `SNESSolve` to solve PDEs. During the iterative process, PETSc prints the norm of the SNES function at each iteration. I would like to understand what this SNES function norm actually represents. I tried computing it myself after the solution was obtained, but I couldn’t match the value reported by PETSc.

My question may be naive, but I am new to FreeFEM/PETSc-based computations, and I couldn’t find detailed documentation on this topic.

Thank you for your help!

Best regards,

Ilyan

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**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [July 11, 2025, 3:53pm UTC](https://community.freefem.org/t/snes-function-norm-meaning/4001/2 "2025-07-11T15:53:07Z")

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PETSc displays the norm of the vector `F(u)`.