function [popm]=mutate(pop,pm,bound,mut_size)
[pop_size,chrom_size]=size(pop);
pop_mut=pop;
pop_total=pop_size*chrom_size;
r=rand(pop_size,chrom_size); k=1;
for i=1:1:mut_size
   r=ceil(pop_size*rand);
   for j=1:1:chrom_size
         ra=rand(12,1);
         s=sum(ra);
         pop_mut(r,j)=pop_mut(r,j)+1*(s-6)*(bound(j,2)-bound(j,1))/6;
         if pop_mut(r,j)<bound(j,1)
            pop_mut(r,j)=bound(j,1);
         else if pop_mut(r,j)>bound(j,2)
               pop_mut(r,j)=bound(j,2);
            end
         end
         popm(i,:)=pop_mut(r,:);
   end;
end;