[Emanuel Camacho]

Good day,

I am trying to read some data from the forces report file that Fluent generates into a UDF but all values appear 0 in Fluent.

I attached 3 figures to illustrate the data file (no 1), the UDF code (no 2), and the message observed in Fluent (no3).

What can I be doing wrong? Do I need to add something else to the code since I am using file-related functions (fscanf and such)?

EDIT: Moved to the Fluent UDF and Scheme Programming Subforum.

[LuckyTran]

Two things come to mind
1) How are all the 12 variable declared? Are they declared as doubles or floats? Are they initialized to 0? If so, can you initialize them to 3.14159 to debug?
2) It's possible fscanf is stuck on the line at timestamp 0 with 12 0's and ending with a \n and it is not going to the next line.

If your code now spits out 3.14159 we know nothing is being read, or it is being read and not being written to memory.
If the code spits out all 0's again, we know it's stuck on the line.

[Emanuel Camacho]

Originally Posted by LuckyTran

Two things come to mind
1) How are all the 12 variable declared? Are they declared as doubles or floats? Are they initialized to 0? If so, can you initialize them to 3.14159 to debug?

Variables are declared as real which I assume are doubles. I did as you said, and initialized them to 3.1415.

Originally Posted by LuckyTran

2) It's possible fscanf is stuck on the line at timestamp 0 with 12 0's and ending with a \n and it is not going to the next line. If your code now spits out 3.14159 we know nothing is being read, or it is being read and not being written to memory. If the code spits out all 0's again, we know it's stuck on the line.

After doing as you said, the results are shown below.

control: 1 | timestep: 0 | flowtime: 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500
control: 2 | timestep: 0 | flowtime: 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500
control: 3 | timestep: 0 | flowtime: 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500
control: 4 | timestep: 0 | flowtime: 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500
control: 5 | timestep: 0 | flowtime: 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500
control: 6 | timestep: 0 | flowtime: 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500 | 3.141500
.
.
.

So, as you said nothing is being read or being read and not written to memory. What should I do?

[LuckyTran]

Can you like maybe give more than 2 lines of your UDF?

It's really hard to debug something assuming you've done everything correctly, when nothing is working correctly.

Like, where is the fprintf even being nested... At this point, I bet you could hard code timestep=2021; into this for loop and it would still print timestep = 0.

[Emanuel Camacho]

Sure, here it is. Thank you for the help.

EDIT: I added this

if (file_forces == NULL)
Message0("FILE WAS NOT OPENNED!\n");
else
Message0("CONTINUING!\n");

and Fluent showed the first option meaning that the file is not being opened! Can it be the file directory?

Code

[AlexanderZ]

problem could be in communication between host and nodes

         #if !RP_NODE
                fscanf(file_forces,"%d %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf %lf",&timestep,&flow_time,&C_D_1,&C_L_1,&C_M_1,&C_D_2,&C_L_2,&C_M_2,&D_f_1,&L_f_1,&D_f_2,&L_f_2);
                #endif

                Message0("control: %d | timestep: %d | flowtime: %lf | %lf | %lf | %lf | %lf | %lf | %lf\n",contr,timestep,flow_time,C_D_1,C_D_2,C_L_1,C_L_2,C_M_1,C_M_2);

here you are reading on host, but asking to print from node_0 which doesn't have information

so you should transfer data from host to nodes


also I can see C_T and C_P variables in your code, which could be a problem as fluent already uses these names for temperature and pressure
I recommend you to use other names

[Emanuel Camacho]

Originally Posted by AlexanderZ

so you should transfer data from host to nodes

How can I do such a thing? I am very sorry but when it comes to this topic I am pretty info-excluded.

Originally Posted by AlexanderZ

also I can see C_T and C_P variables in your code, which could be a problem as fluent already uses these names for temperature and pressure
I recommend you to use other names

Done.

[Emanuel Camacho]

I used this code, and it seems to be working. Will do some more testing.

host_to_node_int_1(timestep);         
host_to_node_real_7(flow_time,C_D_1,C_L_1,C_M_1,C_D_2,C_L_2,C_M_2);
host_to_node_real_4(D_f_1,L_f_1,D_f_2,L_f_2);

Thank you guys!

[LuckyTran]

add this after fopen to make sure the file is actually opened for reading

if (file_forces == NULL)
printf("*\nCANNOT OPEN THE FILE\n*")

else
printf("*\n File ID is %d\n", file_forces);

You can use Message if you don't like printf

another thing you can do is check the return value of fscanf each time it is called. fscanf returns an integer for the number of assigned inputs and returning EOF if it doesn't.

int banana1, banana2, number;
number = fscanf(fp, "%d", banana1)
// number will be 1 if this works
number = fscanf(fp, "%d %d", banana1, banana2)
// number will be 2 if this works

You should have 12 if your code works as intended. But we currently have the suspicion that it's not working, so it won't.

[Emanuel Camacho]

Thank you LuckyTran and AlexanderZ for helping me out.

By passing information from the host to the nodes, the problem was solved.

 
host_to_node_int_1(timestep);         
host_to_node_real_7(flow_time,C_D_1,C_L_1,C_M_1,C_D_2,C_L_2,C_M_2);
host_to_node_real_4(D_f_1,L_f_1,D_f_2,L_f_2);

Thanks once again.