Compiled define_dpm_scalar_update not having any effect in fluent
 

I ran a dpm simulation, compiled it with define_dpm_scalar_update function and hooked it as a discrete phase UDF but its not working. Maybe what I did is physically wrong or maybe I used the wrong UDF.
The UDF:
#include "udf.h"
#include "dpm.h"

DEFINE_DPM_SCALAR_UPDATE(update_velocity, cell, thread, initialize, p)
{
real z = TP_POS(p)[2];
real z_vel = TP_VEL(p)[2];
if (z < 1.5)
{
P_VEL(p)[2] = z_vel * 0.05;
}
else
{
P_VEL(p)[2] = z_vel;
}
}

Its working, just needed to compile using built in compiler.