# Solution u is known but still I am getting an error for H1 norm due to dx(u) term. Why?

**URL:** <https://community.freefem.org/t/solution-u-is-known-but-still-i-am-getting-an-error-for-h1-norm-due-to-dx-u-term-why/2907>\
**Category:** General Discussion\
**Created:** [January 25, 2024, 11:12am UTC](https://community.freefem.org/t/solution-u-is-known-but-still-i-am-getting-an-error-for-h1-norm-due-to-dx-u-term-why/2907 "2024-01-25T11:12:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![RaghunathBandha](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/raghunathbandha/32/1843_2.png) [@RaghunathBandha](https://community.freefem.org/u/RaghunathBandha)\
**Post date:** [January 25, 2024, 11:12am UTC](https://community.freefem.org/t/solution-u-is-known-but-still-i-am-getting-an-error-for-h1-norm-due-to-dx-u-term-why/2907/1 "2024-01-25T11:12:06Z")

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[exampleofdisk.edp](https://community.freefem.org/uploads/short-url/1701ykG0Z65ywKS1HFmo8qLQ9MS.edp) (1.4 KB)

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**Author:** ![marchywka](https://avatars.discourse-cdn.com/v4/letter/m/ee59a6/32.png) [@marchywka](https://community.freefem.org/u/marchywka)\
**Post date:** [January 25, 2024, 1:26pm UTC](https://community.freefem.org/t/solution-u-is-known-but-still-i-am-getting-an-error-for-h1-norm-due-to-dx-u-term-why/2907/2 "2024-01-25T13:26:45Z")

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I didn’t bother to diff it but the derivatives apparently are defined by the element  
and mesh. The integral just specifies the mesh. I only replaced the derivatives but you can  
replace the value term too. Also just a coding note, you use “pow(float,int)” with small int  
and only want  
an int. I’m not use of the guarantee about getting an int back but floating point.  
AFAICT FF does not support “\<\<” for shift but repeated int multiplies may be worth considering.  
.

[exampleofdisk.edp](https://community.freefem.org/uploads/short-url/dBhi0n1xu4elli2FvcU6um9frS1.edp) (1.5 KB)