Date: Fri, 11 Apr 2008 15:44:19 -0400
Reply-To: Ya Huang <ya.huang@AMYLIN.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: Ya Huang <ya.huang@AMYLIN.COM>
Subject: Chance that ranuni generate two identical random numbers?
I wonder what's the chance that ranuni, when given a fixed seed, will
generate 2 identical random number. It seems that ranuni number is
accurate to 14 decimal place. Does it mean that one seed if used more
that 10E14 times will start to repeat the itself?
I tested with one million records, and found no duplicate:
35 data xx;
36 do i=1 to 1E6;
40 format r best32.;
NOTE: The data set WORK.XX has 1000000 observations and 2 variables.
NOTE: DATA statement used:
real time 0.56 seconds
cpu time 0.45 seconds
43 proc print data=xx (obs=5);
NOTE: There were 5 observations read from the data set WORK.XX.
NOTE: PROCEDURE PRINT used:
real time 0.00 seconds
cpu time 0.00 seconds
46 proc sql;
47 select *
48 from xx
49 group by r
50 having count(*) > 1
NOTE: The query requires remerging summary statistics back with the
NOTE: No rows were selected.
When I tried to do 1E14, it took too long. So I killed it.