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Random

Posted on 2000-04-05
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Last Modified: 2010-04-04
I need to create random numbers.

the output of

for n := 0 to 100 do
begin
   Randomize;
   x := Random ( 50 );
   TMemo.Lines.Add ( IntToStr ( x ) );
end;

often looks like this:

5
5
5
5
5
5
33
33
33

how to avoid this and generate "real" random numbers?

like this:

34
7
29
44
2
17

By the way: I'm running a PIII500Mhz,
so I thought of the machine being too fast (Randomize has something to do with the system time) so I added some
Sleep ( Random (20) * Random (20));
Lines, but still no help.

A "Sleep ( 3000 );" does help, but makes it realy slow!

Regards, Oli
0
Comment
Question by:Oli2
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9 Comments
 
LVL 3

Accepted Solution

by:
ckaneta earned 100 total points
ID: 2687758
put randomize outside of the loop
0
 
LVL 1

Author Comment

by:Oli2
ID: 2687765
Edited text of question.
0
 
LVL 6

Expert Comment

by:DrDelphi
ID: 2687766
Move Randomize outside of the for loop:

var n,x:integer;
begin
   Randomize;

for n := 0 to 100 do
begin
   x := Random ( 50 );
   Listbox1.items.Add ( IntToStr ( x ) );
end;


end;


Good luck!!


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LVL 3

Expert Comment

by:hagur
ID: 2687769
Try this:

for n := 0 to 100 do
begin
   Randomize;
   x := Random ( 50 );
   Memo1.Lines.Add ( IntToStr ( x ) );
   Sleep(100);
end;

or even

for n := 0 to 100 do
begin
   Randomize;
   x := Random ( 50 );
   Memo1.Lines.Add ( IntToStr ( x ) );
   Sleep(500);
end;

This works perfectly for me, although on a slower machine, but hey ... a delay is a delay :)

-H
0
 
LVL 1

Author Comment

by:Oli2
ID: 2687770
Hi, ckaneta!

It seems you're right!!!
How come this behaviour?
Can you explain it?
(just being curious)

Regards, Oli
0
 
LVL 17

Expert Comment

by:inthe
ID: 2687791
from delphi help:(see last paragraph)

Initializes the random number generator with a random value.

Unit

System

Category

random number routines

procedure Randomize;

Description

Randomize initializes the built-in random number generator with a random value (obtained from the system clock). The random number generator should be initialized by making a call to Randomize, or by assigning a value to RandSeed.

Do not combine the call to Randomize in a loop with calls to the Random function. Typically, Randomize is called only once, before all calls to Random.
0
 
LVL 1

Author Comment

by:Oli2
ID: 2687808
hmm, okay.
Now my problem: who to give the points to?
Suggestions?
I think of giving them to ckaneta - he was the first...
Is that okay with everybody?

Oli
0
 
LVL 1

Expert Comment

by:umulig
ID: 2689047
ckaneta was first he should get the points.

Umulig
0
 
LVL 1

Expert Comment

by:sageryd
ID: 2689350
Agree! ckaneta was first. Does anyone have an idea on how the random function works? Is there any documentation about it somewhere? You don't have to answer asthough it wasn't I that put up the original Q.
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