# Getting problem in Adaptive Residual based FreeFem++ code of Poisson equation from FreeFem++ doccumentation

**URL:** <https://community.freefem.org/t/getting-problem-in-adaptive-residual-based-freefem-code-of-poisson-equation-from-freefem-doccumentation/3823>\
**Category:** General Discussion\
**Created:** [March 27, 2025, 3:09pm UTC](https://community.freefem.org/t/getting-problem-in-adaptive-residual-based-freefem-code-of-poisson-equation-from-freefem-doccumentation/3823 "2025-03-27T15:09:53Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Monirul25](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/monirul25/32/3287_2.png) [@Monirul25](https://community.freefem.org/u/Monirul25)\
**Post date:** [March 27, 2025, 3:09pm UTC](https://community.freefem.org/t/getting-problem-in-adaptive-residual-based-freefem-code-of-poisson-equation-from-freefem-doccumentation/3823/1 "2025-03-27T15:09:54Z")

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Dear all expert and respected professors, i am wondering why the following **adaptive FF++ codes of Poisson equation which i have just taken from the following tutorial of FreeFem++** documentation does not giving good order of convergence with a very simple test problem.

> **[Static problems](https://doc.freefem.org/models/static-problems.html#metric-adaptation-and-residual-error-indicator)**

( **Metric Adaptation and residual error indicator for P2 and Adaptation using residual error indicator for P1** )

Here, all the codes:  
[Poisson\_P1-adapt.edp](https://community.freefem.org/uploads/short-url/54ZmptVa5tHbwbUCCewtIHH0ije.edp) (4.9 KB)  
[Poisson\_adapt\_P1\_with\_Dx.edp](https://community.freefem.org/uploads/short-url/jy5ma89qfGYgbjnb54FgCdesL8N.edp) (3.9 KB)  
[Poisson-P2\_adapt.edp](https://community.freefem.org/uploads/short-url/eTBzwzSlHyLOFaiEYMDQJeihonm.edp) (3.2 KB)  
[Poisson\_adapt\_P1\_with\_Dx.edp](https://community.freefem.org/uploads/short-url/jy5ma89qfGYgbjnb54FgCdesL8N.edp) (3.9 KB)

I am not getting where i am doing mistakes!. I will be very grateful if i get any suggestions regarding this.

Thanks in advance!.