Reply To: Need help with UDF. “999999: mpt_accept: error: accept failed: No error.”

[Rob]

i , i+1 , i++ are generally integers and used to count up for "something". I'm not sure you should be using them like that in  F_PROFILE(f, t, i+1)  as i may be the surface ID: check the macro. 

In a steady case you're trying to update a boundary at each iteration so effectively you're changing the problem. If there's no damping you may find you oscillate around a value until the solver fails. 

Rather than trying to write ever more complex code, take a step back and figure out exactly what you're trying to acheive. Can it be done by running a model and manually altering a value to then run it again?