[PATCH] libstdc++: add uniform on sphere distribution

[Paolo Carlini]

Hi,

On 07/13/2014 06:03 PM, Ulrich Drepper wrote:
> On Sun, Jul 13, 2014 at 11:43 AM, Paolo Carlini
> <paolo.carlini@oracle.com> wrote:
>> and I think: the normal distributions in x and y do have a non-trivial state
>> (_M_saved, _M_saved_available) which, at any given moment, is different in x
>> and y. Then the trivial inserter of x is called and the trivial extractor of
>> y is called, nothing changes in y. I don't see how the following invocations
>> of y(g) can produce the same sequence of numbers that would be produced by
>> invocations of x(g).
> Remember: we are talking about distributions, not RNGs.
>
> The distribution has no parameters so given the same input (i.e.,
> random byte sequences) it will create the same output all the time.
Sorry, I still don't get it. When operator() of x and y, two 
uniform_on_sphere_distribution, call _M_n(__urng) and those _M_n have a 
different state, the numbers produced are in general different. For 
example, suppose _M_saved_available is true in both _M_n, everything is 
already "decided", no RNGs are involved.

Paolo.