[SciPy-dev] random.set_state also in need of EXPERT attention

[David Goldsmith]

Okee-dokee, thanks!

DG

--- On Tue, 7/28/09, Robert Kern <robert.kern at gmail.com> wrote:

> From: Robert Kern <robert.kern at gmail.com>
> Subject: Re: [SciPy-dev] random.set_state also in need of EXPERT attention
> To: "SciPy Developers List" <scipy-dev at scipy.org>
> Date: Tuesday, July 28, 2009, 1:34 PM
> On Tue, Jul 28, 2009 at 15:16, David
> Goldsmith<d_l_goldsmith at yahoo.com>
> wrote:
> >
> > --- On Tue, 7/28/09, Robert Kern <robert.kern at gmail.com>
> wrote:
> >
> >> Goldsmith<d_l_goldsmith at yahoo.com>
> >> wrote:
> >> >
> >> NR is old and stodgy. They don't cover the
> state-of-the-art
> >> for many arts. Ignore them.
> >
> > Understood.  (Still, I'm looking at the 2007 edition
> - very disappointing.  Well, at least I know now not to
> invest my money in a copy for myself.)
> >
> >> What "expert attention" is required?
> >
> > Quoting Ralf from the Discussion section:
> "[random.set_state] needs some expert explanation of what
> the tuple elements mean, and an example of how to use this
> function to modify the generator state in a meaningful way.
> [later] [Matsumoto/Nishimura, 1997] is reasonably clear,
> there's a link to it on the Wikipedia page. I think it will
> only give you elements 2 and 3 though, 4 and 5 were added
> later in the implementation and I guess are for some of the
> distributions in the random module. [Perhaps irrelevant if
> one doesn't need to decipher the code to write an
> intelligible docstring] The other difficulty is the
> Pyrex/Cython source, a bit harder to read than plain
> Python."
> 
> What is wrong with the current docstring's explanation of
> the tuple
> elements? If anything, there should be less information.
> People should
> be treating it as an opaque object unless if they are in an
> unusual
> circumstance like trying to match an MT implementation in
> another
> language. In such a circumstance, they really need to go
> source diving
> and understand the code. No amount of documentation is
> suitable for
> that.
> 
> But basically, element 4 is a boolean flag (encoded as an
> int) for
> whether element 5 is a cached value for the Gaussian
> distribution or
> not. The Gaussian generator generates two values at a time,
> so we
> return one and cache one and turn on the flag. The next
> call returns
> the cached value and turns off the flag.
> 
> -- 
> Robert Kern
> 
> "I have come to believe that the whole world is an enigma,
> a harmless
> enigma that is made terrible by our own mad attempt to
> interpret it as
> though it had an underlying truth."
>   -- Umberto Eco
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