initial parts
all_1_1_0	1	1
all_2_2_0	1	1
all_3_3_0	1	1
all_4_4_0	1	1
parts with gap
all_1_1_0	1	1
all_2_2_0	1	1
all_3_3_1	0	0
all_4_4_0	1	1
CANNOT_ASSIGN_OPTIMIZE
parts after optimize
all_1_1_0	1	0
all_1_2_1	2	1
all_2_2_0	1	0
all_3_3_1	0	0
all_4_4_0	1	1
parts after detach/attach
all_1_1_0	1	0
all_1_2_1	2	1
all_2_2_0	1	0
all_3_3_1	0	0
all_4_4_0	1	1