mutation.m

一个遗传规划的源程序

function tree = mutation(treein,symbols);

tree = treein;
nn = [length(symbols{1}), length(symbols{2})];
% Mutate one node
[n,v] = tree_size(tree);
i = v(floor(rand*(length(v))+1));
if i<(tree.maxsize+1)/2 & rand<0.5,
  [tree.nodetyp(i) tree.node(i)] = tree_genrndsymb(abs(rand-0.5),nn);
else
  while tree.node(i)==treein.node(i) & tree.nodetyp(i)==treein.nodetyp(i),
    [tree.nodetyp(i) tree.node(i)] = tree_genrndsymb(abs(rand-0.5),nn);
  end
end
return
%------------------------------------------------------------------
function [nodetyp,node] = tree_genrndsymb(p0,nn)

if rand<p0,   
  nodetyp = 2;
else
  nodetyp = 1;
end
node = floor(nn(nodetyp)*rand)+1;
return