Re: [Getfem-users] gradient interpolation matrix

[Yves Renard]

Dear Edouard,

No, unfortunately, there is no function in Getfem that gives the interpolation 
matrix for a derivative of a field. You can perform the interpolation itself 
with the high level generic assembly, but it does not give an interpolation 
matrix. If you want to interpolate on a discontinuous fem, you can instead 
compute the projection matrix which will be easy to invert because it will be 
local (a small matrix on each element). Then if your projection is exact, then 
the inverse will also be an interpolation matrix ...

Best regards,

Yves.



----- Original Message -----
From: "EDOUARD OUDET" <address@hidden>
To: address@hidden
Sent: Friday, November 3, 2017 11:43:34 AM
Subject: [Getfem-users] gradient interpolation matrix

Dear all, 
Is there a way with the getfem python interface to assembly the matrix 
associated to the interpolation matrix of a first derivative evaluation of a 
fem (or its full gradient). 
I found 

Mi = asm_interpolation_matrix(MeshFem mf, vec pts) 

for the evaluation of the function u = MeshFem mf itself, but I was not able to 
identify the relevant generalization for derivatives of u: \partial u_x, 
\partial u_y, etc. 
Thanks a lot for this great library, 
best, Edouard. 

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