thanks. that's good stuff.
man as always this list rocks!!!!
....tony
r e v o l u t i o n w e b d e s i g n
[EMAIL PROTECTED]
www.revolutionwebdesign.com
its only looks good to those who can see bad as well
-anonymous
-----Original Message-----
From: Samuel R. Neff [mailto:[EMAIL PROTECTED]
Sent: Friday, January 23, 2004 6:18 PM
To: CF-Talk
Subject: RE: randomize()
When either rand() or randRange() is used for the first time in a
request, a random number generator is instantiated using the value of
getTickCount() as the seed. This same random number generator is used
for all rand(), randRange(), and randomize() calls for the remainder of
the request.
So, randomize() does affect both rand() and randRange().
To prove it, see this code:
<cfoutput>
<cfloop index="i" from="1" to="10">
<code>#randRange(1, 9)#</code><br />
</cfloop>
<hr />
<cfset randomize(1)>
<cfloop index="i" from="1" to="10">
<code>#randRange(1, 9)#</code><br />
</cfloop>
</cfoutput>
The code calls randomize with a fixed seed. As a result, the results
from randRange are completely predictable and are the same with each
request.
I'm not sure why the docs say to use randomize() before rand() but not
randRange(), or really why they say to use randomize() at all since the
standard methodlogy is to call it with some derivative of getTickCount()
as the argument and the original getTickCount() is how the generator is
created in the first place.
In fact, I've found better results by not calling randomize() at all.
The issue is you can't actually pass getTickCount() to randomize()
because
randomize() only accepts a java int, but in reality the underlying
random number generator uses a java long so while CF can internally pass
getTickCount() directly to randomize() we CF'ers can not.
One first reaction would be to just divide getTickCount() by a number to
reduce the value to within the allowable limits. Given the following
code:
<cfoutput>
<cfloop index="i" from="1" to="10">
<code>#rand()#</code><br />
</cfloop>
<hr />
<cfset randomize(getTickCount()/1000)>
<cfloop index="i" from="1" to="10">
<code>#rand()#</code><br />
</cfloop>
</cfoutput>
The numbers on top of the line are random across requests whereas below
the line will repeat if you refresh quickly. So instead you can use
this code:
<cfoutput>
<cfloop index="i" from="1" to="10">
<code>#rand()#</code><br />
</cfloop>
<hr />
<cfset randomize(right(getTickCount(), 9))>
<cfloop index="i" from="1" to="10">
<code>#rand()#</code><br />
</cfloop>
</cfoutput>
Which will give you more random numbers than using getTickCount()/1000
but still less random than leaving the default.
Perhaps you can get more random numbers by creating an instance of
java.util.Random and storing it in the application scope so you're using
the same generator across requests instead of a new one seeded at the
beginning of each request. Maybe someone with more Java experience can
confirm or refute this possibility.
HTH,
Sam
-----------------------------------------------
Blog: http://www.rewindlife.com
Charts: http://www.blinex.com/products/charting
-----------------------------------------------
> -----Original Message-----
> From: Tony Weeg [mailto:[EMAIL PROTECTED]
> Sent: Friday, January 23, 2004 3:24 PM
> To: CF-Talk
> Subject: randomize()
>
> does randomize do anything for randRange(), or ONLY for rand()
>
> thanks.
>
> ...tony
>
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