# "Err" parameter in adaptmesh

**URL:** <https://community.freefem.org/t/err-parameter-in-adaptmesh/1370>\
**Category:** General Discussion\
**Created:** [December 7, 2021, 9:46am UTC](https://community.freefem.org/t/err-parameter-in-adaptmesh/1370 "2021-12-07T09:46:47Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ruffi92](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/ruffi92/32/921_2.png) [@ruffi92](https://community.freefem.org/u/ruffi92)\
**Post date:** [December 7, 2021, 9:46am UTC](https://community.freefem.org/t/err-parameter-in-adaptmesh/1370/1 "2021-12-07T09:46:47Z")

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I try to make a comparison between the adaption with the command “adaptmesh” (that use the hessian method) and one that use the recovery-gradient method with zienchiewiz-zhu estimator (developed by myself).

But i don’t understand exactly what “err” parameter indicates in adaptmesh.

In the second case i set the “tol” parameter as the approximation of the H1-seminorm of the discretization error, and i would like to set the same also in the first case.

And if i want to set the number of elements (and not the error) during the adaptive procedure? Is it possible?

Thanks in advance for any help!