RE: SQL RAND function question

Loyd,

Use floor(rand() * 11.99999) to get 0-11.

Charles Wilt
Software Engineer
CINTAS Corporation - IT 92B
513.701.1307

wiltc@xxxxxxxxxx

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-
bounces@xxxxxxxxxxxx] On Behalf Of lgoodbar@xxxxxxxxxxxxxx
Sent: Wednesday, February 13, 2008 10:34 AM
To: midrange-l@xxxxxxxxxxxx
Subject: RE: SQL RAND function question

Hi Luis,

Changing to floor() made no appreciable difference. Here is the revised
program and results. The workaround I see so far is to calculate 0-12,
but use only 0-11. The results for the topmost number are so small they
would not skew the distribution.

d x s 10i 0 inz
/free
exec sql set option commit=*none;
for x = 1 to 10000;
exec sql insert into loyd/randno (number)
values(floor(rand()*11));
endfor;
*inlr = *on;
return;
/end-free

10,000:
....+....1....+....2....+....3
NUMBER COUNT ( * )
0 931
1 934
2 922
3 913
4 906
5 896
6 908
7 934
8 851
9 920
10 884
11 1
******** End of data ********

100,000:
....+....1....+....2....+....3
NUMBER COUNT ( * )
0 9,196
1 9,045
2 8,989
3 9,204
4 9,174
5 8,925
6 9,169
7 9,122
8 9,162
9 8,921
10 9,091
11 2
******** End of data ********

1,000,000:
....+....1....+....2....+....3
NUMBER COUNT ( * )
0 90,792
1 91,277
2 90,710
3 91,019
4 90,531
5 91,222
6 90,865
7 90,754
8 90,962
9 90,898
10 90,947
11 23
******** End of data ********


Loyd Goodbar
Senior programmer/analyst
BorgWarner
TS Water Valley
662-473-5713

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Luis Colorado
Sent: Wednesday, February 13, 2008 09:09
To: Midrange Systems Technical Discussion
Subject: RE: SQL RAND function question

Loyd,

This is a bit surprising. Every implementation that I have seen of
rand() or rnd() in other languages gives a random number in the
following range: [0,1)

I would say that maybe there is a bug in the cast to int, which
apparently rounds up to 1 the number 0.99999999... at some unknown
precision.

Would you try this again, using floor() instead of the cast? Something
like

exec sql insert into loyd/randno (number)
values(floor(rand()*11));

It would be interesting to see if the problem is the cast or the rand()
function itself.

Great job!

Luis

--
This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
list
To post a message email: MIDRANGE-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/midrange-l
or email: MIDRANGE-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/midrange-l.

This e-mail transmission contains information that is intended to be confidential and privileged. If you receive this e-mail and you are not a named addressee you are hereby notified that you are not authorized to read, print, retain, copy or disseminate this communication without the consent of the sender and that doing so is prohibited and may be unlawful. Please reply to the message immediately by informing the sender that the message was misdirected. After replying, please delete and otherwise erase it and any attachments from your computer system. Your assistance in correcting this error is appreciated.