[Hosea_Chan]

Dear forum users,

I am working on a DEFINE_ADJUST function to compute the average velocity at the inlet of the cell zone and store the average velocity in the cells with C_UDMI function, which will be used to compute the momentum source term later. The code is as follows:

DEFINE_ADJUST(update,d)
{

	int id_a[cell_zones] = {17,21}; /* get zone id of channel-in later, need input */
	int id_v[cell_zones] = {6,7}; /* get zone id of channel volume later, need input */

	int i;
	for (i=0;i<2;i++) {
		
		#if !RP_HOST
			real A[ND_ND];
			real tfa = 0.0;
			real tfi = 0.0;
			real Ux = 0.0;
			face_t f;
			cell_t c;


			Thread* t1=Lookup_Thread(d,id_a[i]);
			Thread* t2 = Lookup_Thread(d,id_v[i]);


			begin_f_loop(f, t1)
			{
				if PRINCIPAL_FACE_P(f,t1)
				{				
					F_AREA(A,f,t1);
					tfa += NV_MAG(A); 
					/* summing the x-velocity of face */
					tfi += F_U(f,t1)*NV_MAG(A);
				}
			}
			end_f_loop(f, t1)

			tfi=PRF_GRSUM1(tfi);
			tfa=PRF_GRSUM1(tfa);
			Ux = tfi / tfa;
			Message0("Average zone %d U:%12.4e\n",i, Ux);
			Message0("Begin store c loop %d.\n",i);
			begin_c_loop(c,t2)
			{
				if (FLUID_THREAD_P(t2) && NNULLP(THREAD_STORAGE(t2, SV_UDM_I)))
				{
					C_UDMI(c,t2,1) = Ux;
				}
			}
			end_c_loop(c,t2)
			Message0("End store c loop %d.\n",i);
		#endif		
	} 
}

However, I get a SIGSEGV error when I run the code. After isolating the code part by part, it seems that the line "C_UDMI(c,t2,1) = Ux;" is causing the problem as the code runs fine if I commented the line. I have reserved UDM slots in the Fluent GUI. I also used C_UDMI(c,t2,0) for storing the total volume in the DEFINE_INIT code earlier:

DEFINE_INIT(initialize,d)


{
	#if !RP_HOST
		real total_volume[cell_zones];
		//Domain* d;
		
		int i;
		d = Get_Domain(1);
	
		for (i=0; i<2 ; i++) 
		{
			cell_t c;
			Thread* t2 = Lookup_Thread(d,id_v[i]);
			begin_c_loop(c, t2)
			Message0("Begin volume c loop %d\n",i);
			{
				total_volume[i] += C_VOLUME(c,t2);
			}
			end_c_loop(c, t2)
			#if RP_NODE
				total_volume[i] = PRF_GRSUM1(total_volume[i]);
				
			#endif
			
			Message0("Begin store c loop %d\n",i);
			begin_c_loop(c,t2)
			{
				if (FLUID_THREAD_P(t2) && NNULLP(THREAD_STORAGE(t2, SV_UDM_I)))
				{
					C_UDMI(c,t2,0) = total_volume[i];
				}
			}
			end_c_loop(c,t2)
			
			Message0("total_volume of zone %d: %12.4e\n", i,total_volume[i]);
			
		}

		
	#endif /* !RP_HOST */
	
}

It used to cause SIGSEGV as well, but with reference to another post with similar issue, the line "if (FLUID_THREAD_P(t2) && NNULLP(THREAD_STORAGE(t2, SV_UDM_I)))" seem to have solved the problem in the DEFINE_INIT code but not the DEFINE_ADJUST code. A link to the refered post is here: Segmentation fault error in User defined memory UDF

Thank you for your help in advance!

Best regards,
Hosea

[djendara]

usefully you have to lunch the computation without hook the function for one iteration and after hook your udf and try it !