Thanks for explaining!

Please correct if this is wrong understanding:

INITIAL OPTIMIZE RUN with 3 optimize calls:
Parameter 1 optimize--> assume "start" value on P2 and P3 to find optimal P1
Parameter 2 optimize--> use found-optimal P1, P3 "start" to find optimal P2
Parameter 3 optimize--> use found-optimal P1 and P2 to find optimal P3