Re: Simple hash or pseudo-random function

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

On 07/16/2018 10:20 AM, gautier_niouzes@hotmail.com wrote:
> 
> Does someone have a function that would take an integer (range 0 .. 2**63), not uniformily distributed (it's a code with some meaning) and return a number that is pseudo-random, uniformily distributed (could be a floating-point number or an integer in a range of minimum length 365) ?
> The difficulty for me is to find a very simple function. There are many that are for hashing strings, but they could be too time-consuming: it's for a number-crunching program where this function will be called billions of times, so I'm looking for something really simple (and fast :-) ).

Not sure what you mean by "an integer in a range of minimum length 365". You 
could simply use a RNG to generate 64-bit values and xor them with your values 
if you want a 64-bit result. By setting the initial seed, the sequence would be 
repeatable. Ada.Numerics.Discrete_Random would probably serve. If it's too slow, 
the PragmAda Reusable Components includes KISS, a very fast, pretty good RNG. It 
produces 32-bit values, so you'd probably need to call it twice.

-- 
Jeff Carter
"If you don't get the President of the United States on that
phone, ... you're going to have to answer to the Coca-Cola
Company."
Dr. Strangelove
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