Re: Which generator for an 'unsigned long long' ?

[Sven N. Thommesen]

At 11:27 AM 5/28/2000 +0200, you wrote:
> Which is the right
> generator to use and what's the exact syntax to draw an 'unsigned long
> long'  with min==0, with max== ULONG_LONG_MAX ?
> Thanks,
>      
> Fabio


Fabio,

as you will have discovered from the documentation, there is currently no
generator that outputs 64-bit unsigned integers. All the implemented
generators output a number in the range [0,unsignedMax] where unsignedMax
*may* be 2^32-1 (as, for example, with the default generator MT19937).

You *could* fake it by filling a ulonglong with 2 draws from a 32-bit
generator, but then the lower bits will always be functionally tied to
the upper bits. Or, better, you could fill the 64-bit integer with 32-bit
draws from two different generators (best: two generators of different
type, to avoid having two generators of the same type get in sync). But I
don't know what the statistical properties of such combo generators might
be.

Of course, a generator that *did* output an unsigned 64-bit integer would
be a beast to use from java: the automatic translation layer would
promptly interpret this as a *signed* 64-bit integer, since java doesn't
implement unsigned integers.

If you (or anyone else on the list!) have specific requests for things to
add to the random library, please let me know.

Sven Thommesen
address@hidden



                  ==================================
   Swarm-Support is for discussion of the technical details of the day
   to day usage of Swarm.  For list administration needs (esp.
   [un]subscribing), please send a message to

with "help" in the body of the message.