Mathematical Problems in Engineering
Algorithm DCGA
Initialize parent population
𝐹
( individuals) and subpopulation
𝑆
=NULL
While number of iterations < It
max
and number of iterations without improvement < It
𝑛𝑖
Add the ttest individuals in
𝐹
into
𝑆
While the number of individuals in
𝑆
<
Select a subgroup
𝑚
( individuals) without replacement through tournament selection
Set the ttest individual in
𝑚
as a parent
1
and the most dierent individual from
1
as parent
2
Generate ospring from
1
and
2
(crossover, mutation)
Add the generated ospring into
𝑆
Select survivors from
𝑆
and replace all the individuals in
𝐹
with them
Set
𝑆
=NULL
Perform local search on randomly selected individuals among the % ttest individuals in
𝐹
Return the best feasible solution
A : Diversity controlling genetic algorithm.
3.1. Population Initialization. We adopt the permutation rep-
resentation as a chromosome for an individual. For a problem
with orders, a sequence of integers ranging from to
represent a solution where each gene corresponds to an order.
Random key representation [] is applied here to generate
initial chromosome. We rst generate a sequence of random
decimal numbers in (, ) and then sort them in ascending
order. e position of each decimal number in the original
sequence is recorded as an integer, which represents an order.
For example, according to this method, a decimal sequence
(., ., ., ., .) represents an integer sequence (,
, , , ). We randomly generate 2×individuals and select
best half of them as the initial parent population
𝐹
.
3.2. Fitness Evaluation. e processing sequence of each
order is xed according to its position in the chromosome.
e tness evaluation for each chromosome is described as
follows.
(i) Choose next order in the sequence to evaluate until it
has reached the end of the sequence.
(ii) Try to set the start time of chosen order at the earliest
possible start time. e order is accepted if the end
time does not go beyond the deadline and rejected
otherwise. If the chosen order is accepted then the
revenuegainedbyacceptingitisrecorded.Inasit-
uation where order is accepted and order is the
succeeding order to be evaluated, the earliest possible
starttimeoforder is max{
𝑖
,
𝑗
}+
𝑖𝑗
;
𝑖
is the end
time of order .
(iii) e revenue of each accepted order adds to the total
net revenue of the solution.
3.3. Crossover. A crossover operator recombines the genes
of two chromosomes and generates ospring that inherit
part of the characters of the parents. A diversity of crossover
operators have been reviewed by Potts et al. []andby
Poon and Carter []. In this study, we apply the same-site-
copy-rst principle [], which was proposed to solve the
production scheduling problem at rst, to perform crossover
2
2
Parent 1
9
9
1
1
8
∗∗
F : Illustration of crossover with the same-site-copy-rst
principle.
operation in order acceptance and scheduling problem. e
crossover procedure is described as follows.
(i) Any gene code which takes up the same position
of both parents is also xed on that position of the
ospring.
(ii) e remaining positions in the ospring are assigned
by the order of all gene codes in Parent within the
sequence bounded by two randomly selected points.
(iii) e remaining unassigned positions are placed in the
order of appearance in Parent .
e crossover with same-site-copy-rst principle is illus-
trated in Figure .
3.4. Mutation. Mutation is adopted to prevent the newly
formed children from being trapped into their particular
local optima. Several mutation operators have been invented
for permutation problems, such as adjacent two-change, arbi-
trary two-change, arbitrary three-change, and shi-change
[]. Shi-change is applied to the mutation operation here
because it changes the actual positions of some gene codes
to obtain diversity while keeps the relative positions of some
gene codes to inherit gene traits of parents. For a shi-change
procedure, select two positions randomly and replace one
selected position with the other one. en shi all positions
within the sequence bounded by the two selected posi-
tions. e shi-change mutation procedure is illustrated in
Figure .