# Key words: mapu & mapt

**URL:** <https://community.freefem.org/t/key-words-mapu-mapt/683>\
**Category:** General Discussion\
**Created:** [December 11, 2020, 11:18pm UTC](https://community.freefem.org/t/key-words-mapu-mapt/683 "2020-12-11T23:18:42Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![yongxing](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/yongxing/32/3632_2.png) [@yongxing](https://community.freefem.org/u/yongxing)\
**Post date:** [December 11, 2020, 11:18pm UTC](https://community.freefem.org/t/key-words-mapu-mapt/683/1 "2020-12-11T23:18:42Z")

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Dear FreeFEM user,

Can someone tell me the meaning of **mapu=[]** in the following expressoin, unfortunately I cannot find these key words from FreeFEM++ manual.

varf ab( [u,v,p], [lamxh,lamyh,Xh,Yh] ) =  
int2d(Ths, qft=qf9pT, mapu= [Xo,Yo])(  
c1_trace(Grad(lamxh,lamyh)’_(Grad(Xo,Yo)_Grad(u,v)))  
+ c2_(lamxh_u+lamyh_v));

Best wishes,  
Yongxing.

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**Author:** ![frederichecht](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/frederichecht/32/15_2.png) [@frederichecht](https://community.freefem.org/u/frederichecht)\
**Post date:** [December 12, 2020, 10:57am UTC](https://community.freefem.org/t/key-words-mapu-mapt/683/2 "2020-12-12T10:57:22Z")

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I add this fo special scheme, for this article:  
Distributed Lagrange Multiplier for Fluid-Structure Interactions  
with O. Pironneau a A. Boffi

[https://link.springer.com/book/10.1007/978-3-319-94676-4](https://link.springer.com/book/10.1007/978-3-319-94676-4)

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**Author:** ![yongxing](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/yongxing/32/3632_2.png) [@yongxing](https://community.freefem.org/u/yongxing)\
**Post date:** [December 12, 2020, 12:26pm UTC](https://community.freefem.org/t/key-words-mapu-mapt/683/3 "2020-12-12T12:26:22Z")

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Thank you very much Hecht!  
That’s it. Olivier sent me this code.  
I am trying to use interpolation rather than Boffi’s Lagrange Multiplier.  
Yongxing.