crossover.m

一个遗传规划的源程序

function [tree1,tree2] = crossover(treein1,treein2,mode,symbols);

tree1 = treein1;
tree2 = treein2;
nn = [length(symbols{1}), length(symbols{2})];

% Calculate indexes
switch mode,                            % 在这里进行树的交叉类型是 1 就是单点交叉
  case 1,                               % 交叉模式为1时是单点交叉，只在一个分支结点处进行交叉
    [n,v1] = tree_size(tree1);          % n 是tree1 的大小 v1 是结点向量的索引号
    [n,v2] = tree_size(tree2);          % n 是tree2 的大小 v2 是结点向量的索引号
    n = max([tree1.maxsize, tree2.maxsize]);
    dummy1 = zeros(n,1);
    dummy2 = zeros(n,1);
    dummy1(v1) = 1;
    dummy2(v2) = 1;
    v = find((dummy1+dummy2)==2);

    ix1 = v(floor(rand*(length(v))+1));
    ix2 = ix1;
  case 2,                               % 交叉模式为2时是双点交叉，在2个分支结点处同时进行交叉
    [n,v] = tree_size(tree1);
    ix1 = v(floor(rand*(length(v))+1));
    [n,v] = tree_size(tree2);
    ix2 = v(floor(rand*(length(v))+1));
  otherwise,
    return;
end
% 子树的替换，二叉树的重组
sub1 = tree_getsubtree(treein1,ix1);
sub2 = tree_getsubtree(treein2,ix2);
tree1 = tree_inserttree(sub2,tree1,ix1,nn(2));
tree2 = tree_inserttree(sub1,tree2,ix2,nn(2));
return