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Re: Will Math.random return 0.0?

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Am 16.07.2016 um 18:49 schrieb Eric Sosman:

> 
>>   Can we be sure that it will ever terminate?
> 
>     Yes.
> 
No. A couple of well-understood "random" generators are simply of the form

x_n = (x_{n-1} * a) mod b

with a and b some relatively prime numbers. These are not particularly
good generators, but often simple to implement and fast - even more so
if b is (one minus) a power of two.

In such a case, zero is a trivial period of the generator, and for that
reason, the generator is never initialized by zero. It then can be seen
that it never reaches zero either (given the ring Z_b has no zero dividers).

Random() on such a core random generator would return the number x_n
divided by b, and hence the output would never be zero.

Again, whehter this generator is an acceptable generator for Java
implementations I cannot say, but it is at least a well-studied (not-so,
but sufficiently) random generator that has been used in the past.

Greetings,
	Thomas

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Re: Will Math.random return 0.0? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-16 12:49 -0400
  Re: Will Math.random return 0.0? Thomas Richter <thor@math.tu-berlin.de> - 2016-07-16 18:53 +0200
    Re: Will Math.random return 0.0? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-16 13:11 -0400
      Re: Will Math.random return 0.0? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-17 08:06 -0400
    Re: Will Math.random return 0.0? Arne Vajhøj <arne@vajhoej.dk> - 2016-07-16 14:17 -0400

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