Parameter	Explanation of parameter	Setting value/other instructions
R_i	Row number of warehouse, the first row is the lower row near the logistics center, and the second row is the upper row	i = 1, 2
C_i	Column number of warehouse, columns 1 - 33 from left to right	i = 1, 2, …, 33
B_i	Shelf number of the warehouse, which is 1 - 56 from north to south	i = 1, …, 256
P_i	Location number of the warehouse, because one shelf stores one kind of goods, thus B = P	i = 1, 2, …, 56
l_B	Length of each section of the shelf	0.84 m
l_p	Length of each storage location within each section of the shelf	0.84 m
l	Length of the shelf	l = 28 × 0.84 m
Δl	Distance between two rows of shelves	1.68 m
d	Shelf width distance	2.48 m
d_c	Width distance of each column of shelves	1.24 m
W_i	Coordinates of the item i	W_i(x_i, y_i)
S_ij	Distance from item i to item j, where S_ij = S_ji	S_ij = X_ij + Y_ij
X_i	Abscissa distance from item i to item j
Y_i	Ordinate distance from item i to item j
ΔY_i	Distance between item i’s coordinate and the southernmost end of the nearest shelf
T	Total picking time	T = T_i + T_d + T_s + T_t + T_e
T_i	Initialization time for starting the picking	20s
T_d	Picking route time	Determined by picking distance
T_s	Scanning time for a single item after the employee reaches the corresponding item to be picked	Determined by picking distance
T_t	Picking time for picking up and placing each item onto the cart	Determined by picking distance
T_e	Complete the picking task, print and sign to confirm the final time	30s
N_n	Quantity of chromosome population	Determined by order type
P_c	Crossover factor	Determined by order type
P_m	Mutation factor	Determined by order type
round	Maximum number of iterations	Determined by order type