RFR(M): 8044186 Introduce a reproducible random generator

[David Chase]

On 2014-09-22, at 10:09 AM, Sergei Kovalev <sergei.kovalev at oracle.com> wrote:
> 
> On 20.09.2014 00:58, David Chase wrote:
>> I looked hard at Utils.java, that code looks fine.
>> 
>> A question about BMITestRunner.java — I see
>> 76         int seed = Utils.getRandomInstance().nextInt();
>> …
>> 146                 "-D" + Utils.SEED_PROPERTY_NAME + "=" + seed,
>> 
>> But is it guaranteed that
>>    (new Random(seed)).nextInt() == seed?
>> which is what I think this accomplishes?
>> 
>> I just checked, it seems not to be true, so this is not correct re-run advice.

> Did you add -Dc.o.j.testlibrary.random.seed=<somevalue> to the command line?
> 
> To verify please run below class:
> 
> public class NewClass {
>     static long seed = -1;
> 
>     public static void main(String[] args) {
>         System.out.println(new Random(seed).nextInt());
>     }
> }
> 
> In my case it always printing out value: 1155099827

Right.  If the seed is -1, nextInt is 1155099827.
And your program takes that value (1155099827) and
tells you to use it as a seed to reproduce the run.
If you do that, the next seed is 1155099827, not -1,
and the first call to nextInt will return 1494043703.




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