A Global Multilevel Thresholding Using Differential Evolution Approach

Algorithm 2

Onlooker and ranking-based vector selection for DE.

(1)  Input: The target vector index 𝑖, the last index of onlooker 𝑟₁, and 𝛽   ⇐

(2)  Output: The selected vector indexes 𝑟₁,𝑟₂,𝑟₃

(3)  𝑟₁=𝑟₁+1; if 𝑟₁>NP then 𝑟₁=1; end if               ⇐

(4)  while minprop(𝛽)>𝑝_𝑟1//onlooker-like selection         ⇐

(5)     𝑟₁=𝑟₁+1; if 𝑟₁>NP then 𝑟₁=1; end if              ⇐

(6)  end while

(7)  Randomly select 𝑟₂∈{1,NP} //terminal vector index

(8)  while rndreal[0,1)>𝑝_𝑟2 or 𝑟₂==𝑖 or 𝑟₂==𝑟₁ do

(9)     Randomly select 𝑟₂∈{1,NP}

(10) end while

(11) Randomly select 𝑟₃∈{1,NP} //the other vector index

(12) while 𝑟₃==𝑟₂ or 𝑟₃==𝑟₁ or 𝑟₃==𝑖 do

(13)    Randomly select 𝑟₃∈{1,NP}

(14) end while