probelm about UDF marco called "CX_Find_Cell_With_Point"
 

Hi, everybody in this wonderful community. :)
My recent research goal is to obtain the scalar values of neighborhood cells around a specific cell.
To realize this, I wrote a UDF coupling CX_Find_Cell_With_Point and begin_c_loop. The UDF tries to obtain the pressure of a neighborhood cell around a specific cell. Unfortunately， the UDF failed to run.
Can anybody give some advice？ The UDF is posted as follows:

#include <udf.h>
#include "cxndsearch.h"

static ND_Search *domain_table = NULL;

DEFINE_ADJUST(test, domain)
{
cell_t c,c1;
Thread *t, *t1;
CX_Cell_Id *cx_cell;
real P[3];
real P_Cell[3];
real PR;
thread_loop_c (t,domain)
{
begin_c_loop(c,t)
{
domain_table = CX_Start_ND_Point_Search(domain_table,TRUE,-1);
C_CENTROID(P_Cell,c,t); /*obtain the postion of specific cell*/
P[0]=P_Cell[0]+0.001; /* obtain the postion of cell on the right side*/
P[1]=P_Cell[1];
P[2]=0;
cx_cell = CX_Find_Cell_With_Point(domain_table,P,0.0);
c1 = RP_CELL(cx_cell);
t1 = RP_THREAD(cx_cell);
domain_table = CX_End_ND_Point_Search(domain_table);
C_UDMI(c,t,0)=C_P(c1,t1); /* storage the value of pressure*/
}
end_c_loop(c,t);
}
}

Hello，friends.
I guess that I found the reason. The issue may come from the wrong use of CX_Start_ND_Point_Search. Whatever, I corrected my UDF. And it works. The corrected UDF is posted here:

#include <udf.h>
#include "cxndsearch.h"
static ND_Search *domain_table = NULL;
DEFINE_ADJUST(test, domain)
{
cell_t c,c1;
Thread *t, *t1, **pt;
CX_Cell_Id *cx_cell;
real P[3];
real P_Cell[3];
real vof;
real dx=0.2e-3; /*mesh size x direction*/
real dy=0.2e-3; /*mesh size y direction*/
domain_table = CX_Start_ND_Point_Search(domain_table,TRUE,-1);
thread_loop_c (t,domain)
{
begin_c_loop(c,t)
{
C_CENTROID(P_Cell,c,t); /*position of speicific cell*/
P[0]=P_Cell[0]+dx; /*position of cell on the right side*/
P[1]=P_Cell[1];
P[2]=0;
cx_cell = CX_Find_Cell_With_Point(domain_table,P,0.0);
if(cx_cell)
{
c1 = RP_CELL(cx_cell);
t1 = RP_THREAD(cx_cell);
pt = THREAD_SUB_THREADS(t1);
C_UDMI(c,t,0)=C_VOF(c1,pt[0]);
}
else
{
C_UDMI(c,t,0)=0;
}
end_c_loop(c,t);
}
}
domain_table = CX_End_ND_Point_Search(domain_table);
}