# The error and convergence order with PETSc

**URL:** <https://community.freefem.org/t/the-error-and-convergence-order-with-petsc/1560>\
**Category:** General Discussion\
**Created:** [February 28, 2022, 6:35am UTC](https://community.freefem.org/t/the-error-and-convergence-order-with-petsc/1560 "2022-02-28T06:35:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Qianrui](https://avatars.discourse-cdn.com/v4/letter/q/9fc348/32.png) [@Qianrui](https://community.freefem.org/u/Qianrui)\
**Post date:** [February 28, 2022, 6:35am UTC](https://community.freefem.org/t/the-error-and-convergence-order-with-petsc/1560/1 "2022-02-28T06:35:46Z")

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Is there an example of calculating the error and convergence order with PETSc？I tried to change an example of a wave equation, but the convergence order result and error result are different from the results of the program written under FreeFem++.