[Getfem-users] Problem using GradGT in assembling boundary condition

[Cédric Venet]

 Hi,

The usage of GradGT is not documented and it is never used. From the 
documentation, GradGT should be the representation of K the gradient of 
the geometric transform. I suppose that it takes two "arguments". First 
the line number (ie the dimension in the problem/real/mesh space) and 
then the column number (ie the dimension in the reference space).

I would like to assemble the condition (on the boundary of a 2D mesh so 
on 1D element):

integral of ( du/dt * v )

with t the tangent vector. I tried numerous formulation around this one:

"M(#1,#1)+=sym(comp(Grad(#1).GradGT().Base(#1))(:,i,i,k,:))"

but none seems to work. for me, i should be summed on {0,1} and k on {0} 
thus giving the formula:

integral of ( (du/dx*dx/dt + du/dy*dy/dt) * v )

the error is in getfem_mat_elem.cc line 364. (in the function 
expand_product_daxpy)
it seems that the vector t is too small and the code try to dereference 
the iterator pt after the end of t.

I tried to understand how t  was sized, wihtout much success. I see that 
adjust_sizes is called numerous times. the last call before the crash is 
with the "array" [4 2 2 2 1] in argument. (my mesh use quad).

Can you help me?

Regards,

Cédric