Using PP_CELL or TP_CELL doesn’t make a difference.I am not sure I understand the difference correctly but from my understanding TP_ should be correct.

I agree, the link the cell is likely the problem. I tested if "cell = TP_CELL(p)" works by outputting "Message(“cellid %d”, cell);" and it looks plausible (values between 0 and my max cell count). For the thread "t0 = TP_CELL_THREAD(tp)" I first checked "if (NULLP(t0)) Message(“Nullpointer”);" and it did not trigger. However "if (NULLP(THREAD_STORAGE(t0,SV_U))) Message(“Nullpointer”);" triggers. From my understanding this should be the location were C_U(c,t) looks for the data.

So I am wondering, if I am referencing a Thread but not the correct one? Or is the storage location wrong? Do I need to account for any Subthreads? I have one Eulerian Phase and one DPM phase in my case.