Error assembling a matrix 3d surface mesh

General Discussion
1

Hello,
I came across a segmentation fault when trying to get a matrix from varf when using a 3d surface mesh. The following code gives the error, using the torus given as example in the doc. I have tried with both FreeFem++4.5 and the recent 4.6.
Any ideas on how to solve this ?
Thank you.

load"msh3"                                                                                                                                                                               
real R = 3, r=1;                                                                                                                                                                         
real h = 0.2; //                                                                                                                                                                         
int nx = R*2*pi/h;                                                                                                                                                                       
int ny = r*2*pi/h;                                                                                                                                                                       
func torex= (R+r*cos(y*pi*2))*cos(x*pi*2);                                                                                                                                               
func torey= (R+r*cos(y*pi*2))*sin(x*pi*2);                                                                                                                                               
func torez= r*sin(y*pi*2);                                                                                                                                                               
meshS ThS=square3(nx,ny,[torex,torey,torez],orientation=-1) ;                                                                                                                            
                                                                                                                                                      
fespace Vh(ThS,[P1,P1]);                                                                                                                                                                 
                                                                                                                                                                                     
macro grad(u) [dx(u),dy(u),dz(u)] //EOM                                                                                                                                                  
                                                                                                                                                                                     
func f1 = 10;                                                                                                                                                                            
func f2 = -15;                                                                                                                                                                           
                                                                                                                                                                                     
varf vP([u1,u2],[v1,v2]) = int2d(ThS)(grad(u1)'*grad(v1)+ grad(u2)'*grad(v2)) - int2d(ThS)(f1*v1+f2*v2);                                                                                 
                                                                                                                                                                                     
matrix A = vP(Vh,Vh);
2 
varf vP([u1,u2],[v1,v2]) = int2d(ThS)(grad(u1)'*grad(v1)+ grad(u2)'*grad(v2)) - int2d(ThS)(f1*v1+f2*v2);
3

I corrected the code, thank you.

4

Hi,
Does someone have an explanation for this?
Thank you,
Rémi

5

What is the problem right now?

6

The problem is:

matrix A = vP(Vh,Vh);

provokes a Segmentation fault (core dumped).

7

Not with the correct variational formulation, does it?

8

No, even with the correct formulation (I corrected it in the initial post) the error still arises.
Any other clue?

9

Hello,
I amn’t able to reproduce your bug,
can you give me information about your system please
Do you use binary package or compile FreeFEM?

10

Same for me: I can reproduce the segmentation fault with your initial code, but not with the new one.

11

Thank you for your help.

I have compiled Freefem++ 4.5 on Ubuntu 18.04.

12

Could you please try version 4.6?

13

Alright, it works with the 4.6 installed from the binary package. Thank you very much.