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| From | Arne Vajhøj <arne@vajhoej.dk> |
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Will Math.random return 0.0? |
| Date | Sat, 16 Jul 2016 14:15:33 -0400 |
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On 7/16/2016 12:49 PM, Thomas Richter wrote:
> Am 16.07.2016 um 17:24 schrieb Stefan Ram:
>> I wrote the following program.
>>
>> public final class Main
>> { public static void main( final java.lang.String[] args )
>> { while( java.lang.Math.random() != 0.0 );
>> java.lang.System.out.println( "0.0" ); }}
>>
>> What do you expect it's (average) runtime to be
>> on average hardware?
>>
>> Can we be sure that it will ever terminate?
>
> No, you cannot.
Sure?
> If random() is implemented by the average (=bad) linear
> congruence generator, then zero will never be the output of random().
Not true.
First LCG's can have seed zero and a good cycle as long as the add part
is non-zero.
Second even for an MLCG (with add part zero) where seed can not be
zero, then the random numbers can include zero simply by subtracting
one.
Arne
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Re: Will Math.random return 0.0? Thomas Richter <thor@math.tu-berlin.de> - 2016-07-16 18:49 +0200
Re: Will Math.random return 0.0? Arne Vajhøj <arne@vajhoej.dk> - 2016-07-16 14:15 -0400
Re: Will Math.random return 0.0? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-16 14:19 -0400
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