[tjmartian]

I am trying to find the cell index of a neighboring cell and found the macros F_C0 and F_C1 that look like they would work for me. However, when I try to run the code I get an Access Violation in Fluent. I read through the user manual and believe I am doing it correctly. The code is as follows:

 
#include "udf.h"
#include "metric.h"
#include "stdio.h"
#include "math.h"
#include "stdlib.h"
 
float mass_load[3000];
float mass_load_new[3000];
Domain *dz;
Thread *t;
Thread *t0;
Thread *t1;
Thread *tz;
Thread *tf;
cell_t c, ca, cb, cz;
face_t f;
int j, k;
 
DEFINE_INIT(cell_init, d)
{
double inlet_ml;
inlet_ml = .01;
j=0;
thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
mass_load[j] = inlet_ml;
j++;
}
end_c_loop(c,t)
}
}
　
DEFINE_ADJUST(get_data4, d)
{
real vel[2];
real A[2];
real next_centr[2];
double av_prod, cell_ml;
double mass_load_sum, mass_out_sum;
int i;
 
 
dz = Get_Domain(1);
j=0;
thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
mass_load_sum = 0;
mass_out_sum = 0;
for(i=0; i<4; i++) {
f = C_FACE(c,t,i);
tf = C_FACE_THREAD(c,t,i);
t0 = THREAD_T0(tf);
t1 = THREAD_T1(tf);
ca = F_C0(f,tf);
cb = F_C1(f,tf);
if(c1 != NULL) {
vel[0] = ((C_U(c0,t0) + C_U(c1,t1))/2);
vel[1] = ((C_V(c0,t0) + C_V(c1,t1))/2);
}
else {
vel[0] = 0;
vel[1] = 0;
}
F_AREA(A,f,tf);
av_prod = NV_DOT(vel, A);
if(av_prod < 0) {
C_CENTROID(next_centr, c1, t1);
k = 0;
thread_loop_c(tz,dz)
{
begin_c_loop(cz,tz)
{
if(cz == c) {
cell_ml = mass_load[k];
}
k++;
}
end_c_loop(cz,tz)
}
mass_load_sum += cell_ml * fabs(av_prod);
}
else {
mass_out_sum += fabs(av_prod);
}
}
mass_load_new[j] = mass_load_sum/mass_out_sum;
j++;
}
end_c_loop(c,t)
}
j=0;
thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
mass_load[j] = mass_load_new[j];
j++;
}
end_c_loop(c,t)
}
}

The code compiles fine but when I try to run it I get the error. As soon as I get rid of the F_C0 and F_C1 lines the code runs fine so it would seem that's where the problem is. Is there anything wrong with how I'm using those macros or is there anything else I can try? Thanks for your help.