r=ceilrandps; while j==r防止自己与自己交叉 r=ceilrandps; end

This code generates a random integer between 1 and ps using the rand function and assigns it to the variable r. It then enters a while loop that checks whether the current value of j is equal to the remainder of r divided by ps. This is done to prevent the crossover of an individual with itself. If j is equal to r mod ps, a new random value is generated for r until j is no longer equal to r mod ps. Once a suitable value for r is found, the while loop is exited and the crossover operation can proceed