[Mono-osx] bug in Random

[Miguel De Icaza]

Hello,

> Hello Mono-team... Can you please provide an answer?  Was the  
> intention to use a different algorithm for the Random class, or was  
> that a mistake?  Honestly I cannot see a technical reason to use a  
> different one.

I believe this has been discussed in the past, but I do not remember  
the outcome of the discussion.

If having the same results across platforms is that important to you,  
you should take Mono's implementation (or whatever other open source  
implementation you happen to like) and bundle that with your code so  
that it works the same on Windows and .NET.

I do not believe that we should be in the business of providing a  
random number generator that produces the same random numbers as  
another random number implementation.   That does not sound very  
random to me.

Miguel.

>
> Thanks.
>
> On Mon, Jan 19, 2009 at 5:43 PM, Rodrigo Kumpera <kumpera at gmail.com>  
> wrote:
> Your application depends on an implementation detail of the MS  
> runtime.
> There is no guarantee either that they won't change the Random  
> algorithm.
>
> This is unfortunate to your application but the solution is pretty  
> simple, copy mono's
> implementation to your project and rely on it instead of an external  
> prng.
>
>
>
> On Mon, Jan 19, 2009 at 8:38 PM, MacUser <atlas at spiralgraphics.biz>  
> wrote:
>
> This is also a point of concern for me.  My code , written on  
> Microsoft .NET,
> relied on the fact that using the same seed will always produce the  
> same
> series of numbers.  To port to Mono, not only would I need Mono's  
> Random()
> to be consistant across all Mono platforms, but also consistant to the
> results that Microsoft's Random() produces.
>
> By the way, I work in the algorithmic graphics generation area,  
> where an
> image produced with the same input values must always look the same
> regardless of the platform the app is running on.  This is why  
> reliable
> seeding is so important.
>
>
>
> Rodrigo Kumpera wrote:
> >
> > It doesn't state the the algorithm has to be the same, just that  
> it must
> > be
> > reproducible given the same seed.
> >
> > On Mon, Jan 19, 2009 at 3:27 PM, Duane Wandless <duane at wandless.net>
> > wrote:
> >
> >> That is a valid question.  From MSDN, the Random class is a  
> Pseudo-random
> >> number generator:
> >> The random number generation starts from a seed value. If the  
> same seed
> >> is
> >> used repeatedly, the same series of numbers is generated.
> >>
> >> http://msdn.microsoft.com/en-us/library/system.random.aspx
> >>
> >> The value in this is that given a seed will produce the same  
> sequence of
> >> random numbers.  So if the client and server both know the seed  
> then
> >> the algorithm will work correctly on both platforms.
> >>
> >>
> >> On Mon, Jan 19, 2009 at 12:09 PM, Matt Emson
> >> <memsom at interalpha.co.uk>wrote:
> >>
> >>> Duane Wandless wrote:
> >>>
> >>>> Maybe I incorrectly assume that the pseudo-random number should  
> be the
> >>>> same on both platforms... but I believe that it should be a  
> predictable
> >>>> sequence given the same seed.
> >>>>
> >>> Maybe this is a silly question, but why would you want your  
> *random*
> >>> number to be the same on both platforms, more so "a predictable
> >>> sequence"?
> >>> Sure I'm missing something obvious, but... ?!
> >>>
> >>
> >>
> >> _______________________________________________
> >> Mono-osx mailing list
> >> Mono-osx at lists.ximian.com
> >> http://lists.ximian.com/mailman/listinfo/mono-osx
> >>
> >>
> >
> > _______________________________________________
> > Mono-osx mailing list
> > Mono-osx at lists.ximian.com
> > http://lists.ximian.com/mailman/listinfo/mono-osx
> >
> >
>
> --
> View this message in context: http://www.nabble.com/bug-in-Random-tp21544091p21553211.html
> Sent from the Mono - OSX mailing list archive at Nabble.com.
>
> _______________________________________________
> Mono-osx mailing list
> Mono-osx at lists.ximian.com
> http://lists.ximian.com/mailman/listinfo/mono-osx
>
>
> _______________________________________________
> Mono-osx mailing list
> Mono-osx at lists.ximian.com
> http://lists.ximian.com/mailman/listinfo/mono-osx
>
>
> _______________________________________________
> Mono-osx mailing list
> Mono-osx at lists.ximian.com
> http://lists.ximian.com/mailman/listinfo/mono-osx

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.ximian.com/pipermail/mono-osx/attachments/20090125/cba2dff6/attachment-0001.html