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fatal signal segmentation fault in a UDF

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Old   January 10, 2017, 08:57
Default fatal signal segmentation fault in a UDF
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mohamed hares
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Hello,

when I want to run a simulation with a UDF Fluent 16. I have this error which appears

Error: received a fatal signal (Segmentation fault).
Error Object: #f

After some research on this error, I have found that this error appears when we are trying to Hook the adjust function in FLUENT solver . I don't know why this error appeared -- If I unhook this function - it works well- and if I delete the equations inside the adjust function it also works well

the code :


#include "udf.h"
#include "math.h"
#include "sg_udms.h"
#define rhomax 0.0008
#define phimax 5000
#define debye 0.001
#define rhomax 0.0008
#define phimax 5000
#define sigma 0.003
#define rholoc 0.0005

num {
phi,
rho
};
enum {
Ex,
Ey,
Fx,
Fy,
Fm
};

DEFINE_SOURCE(rho_source, c, t, dS, eqn)
{
real source;
source=-pow(debye,-2)*C_UDSI(c,t,rho);
dS[eqn]=-pow(debye,-2);
return source;
}


DEFINE_PROFILE(rho_profile,thread,i)
{
float r[3];
float x;
real xloc;
face_t f;
begin_f_loop(f,thread)
{
F_CENTROID(r,f,thread);
xloc = r[0];
F_PROFILE(f,thread,i)=exp(-pow((xloc-rholoc),2)/(2*pow(sigma,2)));
}
end_f_loop(f,thread)
}





DEFINE_ADJUST(udf_adjust, domain)
{
Thread *t;
cell_t c;
thread_loop_c(t,domain)
{
begin_c_loop(c,t)
{
C_UDMI(c,t,Ex)=-C_UDSI_G(c,t,phi)[0];
C_UDMI(c,t,Ey)=-C_UDSI_G(c,t,phi)[1];
}
end_c_loop(c,t)
}
}


DEFINE_SOURCE(X_Source, c, t, dS, eqn)
{
real Sourcex;
Sourcex=-rhomax*phimax*C_UDSI(c,t,rho)*C_UDSI_G(c,t,phi)[0];
dS[eqn]=-rhomax*phimax;
C_UDMI(c,t,Fx)=Sourcex;
return Sourcex;

}



DEFINE_SOURCE(Y_Source, c, t, dS, eqn)
{
real Sourcey;
Sourcey=-rhomax*phimax*C_UDSI(c,t,rho)*C_UDSI_G(c,t,phi)[1];
dS[eqn]=-rhomax*phimax;
C_UDMI(c,t,Fy)=Sourcey;
C_UDMI(c,t,Fm)=sqrt(C_UDMI(c,t,Fx)*C_UDMI(c,t,Fx)+ C_UDMI(c,t,Fy)*C_UDMI(c,t,Fy));
return Sourcey;
}

and all memory are located - and all other functions works well
the error just in the udf
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Old   January 11, 2017, 07:08
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mohamed hares
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Hello!

Now I just follow A.Bouchmal's MS thesis "Modeling of Dielectric-Barrier Discharge Actuator".

http://www.lr.tudelft.nl/fileadmin/F...l_Bouchmal.pdf

However, the code which he atteched doesn't works.

I compiled the code and input conditions but when I start calculate, the error "FLUENT recieved fatal signal [segmentation fault] occurs.

after alloct all memory and user define scalar and hooking it
it works well
but at hooking the adjust function the error occurs

Please help me to solve the problem.
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Old   January 11, 2017, 11:36
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I think you need to add the mem.h header to access C_UDSI_G ( I mean put #include "mem.h" on top)
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Old   January 12, 2017, 04:47
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mem.h is sourced through udf.h so that should not be the trouble.

I suppose that num{phi, rho} at the beginning should be enum{phi, rho}, possibly just a typo. A critical one if that were the case though.

Another thing that comes to my mind - if you are using more than one UDF library, you should use Reserve_User_Memory_Vars function.
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Old   January 12, 2017, 07:11
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Quote:
Originally Posted by Zbynek View Post
mem.h is sourced through udf.h so that should not be the trouble.

I suppose that num{phi, rho} at the beginning should be enum{phi, rho}, possibly just a typo. A critical one if that were the case though.

Another thing that comes to my mind - if you are using more than one UDF library, you should use Reserve_User_Memory_Vars function.
Thank for reply
and it is already enum{phi, rho}, , but it was my mistake at coping the code to you
------
I do not know how to use Reserve_User_Memory_Vars function .
Thank you again
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Old   January 20, 2017, 16:41
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ali
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Hares,

Did you solve the problem?
I am having this problem in my own udf. I traced it and it is caused when I want to use C_UDSI_G(c,t,0).
If instead of this I use some constant value, the udf runs well.
Apparently C_UDSI_G is not saved in the memory and thus is not accessible. I tried including mem.h in the header but that did not change anything.
I saw other people in this forum are also having this problem but I could not find any solution.
Have you?

Thanks,
Ali
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Old   January 21, 2017, 03:26
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Quote:
Originally Posted by alinik View Post
Hares,

Did you solve the problem?
I am having this problem in my own udf. I traced it and it is caused when I want to use C_UDSI_G(c,t,0).
If instead of this I use some constant value, the udf runs well.
Apparently C_UDSI_G is not saved in the memory and thus is not accessible. I tried including mem.h in the header but that did not change anything.
I saw other people in this forum are also having this problem but I could not find any solution.
Have you?

Thanks,
Ali
it is solved with me.
the error that I hook adjust in the beginning and I tried hooking it after 1 or 2 iteration ......
my advice for you that if you allocate the memory well
do unhook for the C_UDSI_G in the first iteration because if the value of the scalar did not be solved . so the Gradient of it ( C_UDSI_G ) will have an error
Good Luck
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