[fpc-pascal] 32-bit random numbers

Peter peter at pblackman.plus.com
Fri Apr 21 18:31:32 CEST 2017

On 21/04/17 10:11, Mark Morgan Lloyd wrote:
> Am I correct in interpreting the documentation as implying that if I
> want to get a full-range 32-bit unsigned random number I have to use
> something like Random($100000000) ?
> Internally, that gets a 64-bit random by calling genrand_MT19937 twice
> and throwing away one of the results. Not only does that waste time, but
> it also means that if I use a "well known" seed I only see every other
> value from the expected sequence e.g. http://oeis.org/A221557

For a 32bit unsigned, I would be inclined to use random to a int64, and
mask out the upper bits.

You could also write an XORShift generator if you are prepared to forgo
the presence of zero in the sequence.


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