I am doing solidifcation during jet breakup using coupled VOF and soldification model. The molten jet is quenched by surrounding liquid and the fragments produced during breakup become solid. I am trying to group the solid cells (fragments) formed during solidification  if they are adjacent or connected and number that group. So that the  neighboring solid cells can be grouped as a single solid and assigned with user-input velocity for all the solid cells in that group. There may be separate solid cell group in the domain with corresponding user-input velocity values. For this i have to assign same number (counter) to the adjacent connected solid cells in UDMI to group them a single solid object later while imposing velocity. I have used c_face_loop looping, and the C0 and C1 neigboring cells identifiers to group solid cells. The UDF is working fine when running in single processor. But, while running UDF in multi-processors, the neighboring cells (C0 and C1) search is limited  to partition boundary (of active partitions) only. I can't group the connected solids that are adjacent to partitioned boundary and part of next computer NODEs. The parallel UDF gives separate solid groups even though they are connected, while the series UDF gives a single connected solid group for the same. Please suggest an alternative approach to access the cells of adjacent NODEs and group them in one group. I found that all the NODES run in sync only, not sequentially.