nsga2算法matlab代码
时间: 2023-08-03 16:05:28 浏览: 33
以下是NSGA-II算法的MATLAB代码示例:
```
function [pop, front] = nsga2(pop, N, M)
% pop是种群,N是种群大小,M是目标函数数
[pop, rank] = fast_non_dominated_sort(pop, N, M);
front = 1;
pop_front{1} = rank==1;
crowding_distance = calculate_crowding_distance(pop, pop_front{1}, M);
while sum(cellfun('length',pop_front))<N
front = front + 1;
pop_front{front} = [];
for i = 1:length(pop_front{front-1})
if length(pop_front{front}) >= N-sum(cellfun('length',pop_front))
break;
end
crowding_distance{i} = calculate_crowding_distance(pop, pop_front{front-1}(i,:), M);
pop_front{front} = [pop_front{front}; pop(pop_front{front-1}(i,:))];
end
[pop_front{front}, crowding_distance] = sort_by_crowding_distance(pop_front{front}, crowding_distance);
end
pop = cat(1, pop_front{:});
end
function [pop, rank] = fast_non_dominated_sort(pop, N, M)
F{1} = [];
n(1) = 0;
rank = zeros(N,1);
for p = 1:N
S{p} = [];
n(p) = 0;
for q = 1:N
if dominates(pop(p,:),pop(q,:))
S{p} = [S{p} q];
elseif dominates(pop(q,:),pop(p,:))
n(p) = n(p) + 1;
end
end
if n(p) == 0
rank(p) = 1;
F{1} = [F{1} p];
end
end
i = 1;
while ~isempty(F{i})
Q = [];
for p = F{i}
for q = S{p}
n(q) = n(q) - 1;
if n(q) == 0
rank(q) = i+1;
Q = [Q q];
end
end
end
i = i + 1;
F{i} = Q;
end
pop = pop(rank==1,:);
end
function flag = dominates(x,y)
flag = any(x<y) && all(x<=y) || any(x>y) && all(x>=y);
end
function crowding_distance = calculate_crowding_distance(pop, front, M)
N = size(front,1);
crowding_distance = zeros(N,1);
for m = 1:M
[sorted, index] = sortrows(pop(front,m));
crowding_distance(index(1)) = Inf;
crowding_distance(index(end)) = Inf;
for i = 2:N-1
crowding_distance(index(i)) = crowding_distance(index(i))+(sorted(i+1)-sorted(i-1))/(sorted(end)-sorted(1));
end
end
end
function [pop, crowding_distance] = sort_by_crowding_distance(pop, crowding_distance)
[~, index] = sort(crowding_distance,'descend');
pop = pop(index,:);
crowding_distance = crowding_distance(index);
end
```
这段代码实现了NSGA-II算法的主要功能,包括快速非占优排序、计算拥挤度距离和排序等。根据需要,你可以对其进行修改以适应你的实际问题。