Dear Phuoc,
Do you compute some gradient quantities on the finite element nodes ? If
not, it should not pose any problem since using the generic assembly,
the computation are located on the Gauss points which are not located on
the nodes.
can you extract the smallest possible program on which the error occurs ?
Best regards,
Yves
Le 18/06/2018 à 10:35, Huu Phuoc BUI a écrit :
Dear Yves,
Sorry I email you again on this topics. In fact, the generic assembly
did some computation on pyramid elements but the output is 'nan'. On
elements of others types (of the mixed mesh), the output is fine.
Please let me know if you have an idea. Thanks.
Best regards,
Phuoc
On 15/06/2018 16:43, Huu Phuoc BUI wrote:
Dear Yves,
That's great! It's indeed working now. Thank you very much for your
help.
Best regards,
Phuoc
On 15/06/2018 16:38, Yves Renard wrote:
Dear Phuoc,
The problem is indeed the same, to compute the location of gauss
points on a neighbour element, the inversion of the geometric
transformation is called. This inversion used a Newton algorithm
whose starting point is a node of the element ... (function
find_initial_guess in bgeot_geotrans_inv.cc).
I changed a bit the starting point, so it should work now. But this
is clear that the fact that the transformation is singular at the
pyramid tip is a difficulty.
Best regards,
Yves
Le 15/06/2018 à 11:53, Huu Phuoc BUI a écrit :
Dear Yves,
Thank you very much for your help.
Now it worked when computing the outer faces. But I faced another
problem of this mixed mesh. In fact, I'd like to compute the stress
jump at the inner faces using generic assembly, and GetFEM++ showed
an error like this:
"
File "/usr/local/lib/python2.7/dist-packages/getfem/getfem.py",
line 5591, in asm_generic
return getfem('asm', 'generic', mim, order, expression, region,
model, *args)
RuntimeError: (Getfem::InterfaceError) -- Error in
getfem_generic_assembly_compile_and_exec.cc, line 3887 virtual int
getfem::ga_instruction_neighbour_transformation_call::exec():
Geometric transformation inversion has failed in neighbour
transformation
"
So, as you said, this error comes from geometric transformation of
pyramid elements. Do you have an idea how to fix it?
Best regards,
Phuoc
On 15/06/2018 11:10, Yves Renard wrote:
Dear Phuoc,
The problem come from the fact that the test is made on the mean
unit normal vector on a face. This mean unit normal vector is
computed by averaging the unit normal vector on each geometrical
node of a face. Unfortunately, for a pyramid element, the
transformation is singular on the geometrical nodes.
I replaced the mean of normal vector by the normal vector on the
mean of geometrical nodes of the face. It fixes the problem. (I
push the change on the master branch).
Best regards,
Yves
Le 14/06/2018 à 15:40, Huu Phuoc BUI a écrit :
Dear Yves,
Please find the mesh attached.
Thank you for your help.
Best regards,
Phuoc
On 14/06/2018 14:52, Yves Renard wrote:
Dear Phuoc,
No, I see no reason. If you can just send me the mesh in a
format readable by GetFEM, I could check what is wrong.
Best regards,
Yves
Le 14/06/2018 à 10:24, Huu Phuoc BUI a écrit :
Dear Getfem-users,
I have a problem with computing the outer faces when using a
mixed mesh (having tetras, hexa, prisms and pyramids).
The error is:
face_left = m.outer_faces_with_direction([0, 0., -1.0], 0.01)
File
"/usr/local/lib/python2.7/dist-packages/getfem/getfem.py", line
1372, in outer_faces_with_direction
return self.get("outer_faces_with_direction", v, angle, CVIDs)
File
"/usr/local/lib/python2.7/dist-packages/getfem/getfem.py", line
1152, in get
return getfem('mesh_get',self.id, *args)
RuntimeError: (Getfem::InterfaceError) -- Error in
bgeot_geometric_trans.cc, line 381 const base_matrix&
bgeot::geotrans_interpolation_context::B() const:
Non invertible matrix
Please let me know if you have any idea. Thank you.
Best regards,
Phuoc
--
Yves Renard ([email protected]) tel : (33) 04.72.43.87.08
Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
20, rue Albert Einstein
69621 Villeurbanne Cedex, FRANCE
http://math.univ-lyon1.fr/~renard
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