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#1
August 16th, 2000, 11:50 AM
 JonLed
Contributing User

Join Date: Aug 2000
Location: Indiana
Posts: 614
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For some reason random numbers don't seem to be that random in PHP (at least if the range like 2 numbers). It seems to favor the 1 instead of 2 about 90% of the time.

Anybody know why this is, or how to work around it? (I'd like to have about a 50/50 split.

#2
August 16th, 2000, 12:11 PM
 JonLed
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Nevermind. I forgot to seed the random number.

#3
August 16th, 2000, 12:14 PM
 JBLallement
Junior Member

Join Date: Aug 2000
Location: France
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Hi JonLed,

I don't agree with you.

I've done the following test.
- Generate 1 million numbers between 1 and 2
- Add it to the corresponding array element
- Evaluate the probability

the results:
1: 49.882%
2: 50.118%

Here is the code:
<?
define(MAXLOOP,1000000);
srand((double)microtime()*1000000);

\$arr[1]=0;\$arr[2]=0;

while(\$i++<MAXLOOP)
\$arr[rand(1,2)]++;

echo "1: ".(\$arr[1]/MAXLOOP*100)."%n";
echo "2: ".(\$arr[2]/MAXLOOP*100)."%n";

?>

JBL

#4
August 16th, 2000, 12:21 PM
 JonLed
Contributing User

Join Date: Aug 2000
Location: Indiana
Posts: 614
Time spent in forums: 4 h 49 m 49 sec
Reputation Power: 15
Yes, I know. Read my message above.

srand((double)microtime()*1000000);

Is what I left out. (This seeds the random number).

 Viewing: Dev Shed Forums > Programming Languages > PHP Development > Random Number

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