because the random seed is keep constant,you can try with random seed 0

thank you very much~~ and i found the explanation in the help document:

Random-number functions and CALL routines generate streams of random numbers from an initial starting point, called a seed, that either the user or the computer clock supplies. A seed must be a nonnegative integer with a value less than 231-1 (or 2,147,483,647). If you use a positive seed, you can always replicate the stream of random numbers by using the same DATA step. If you use zero as the seed, the computer clock initializes the stream, and the stream of random numbers is not replicable.

learning，thank you very much~~~

thx for sharing

伪随机数