On Friday, 13 October 2017 11:15:19 PDT Lars Knoll wrote:
> > Well, one of them is deterministic, but only if you know the seed which
> > comes from the non-deterministic one. So it's highly unlikely that you'll
> > be able to determine its sequence.
>
> Of course, but they have different characte
> On 13 Oct 2017, at 16:12, Thiago Macieira wrote:
>
> On Friday, 13 October 2017 01:30:57 PDT Lars Knoll wrote:
>> This sounds like a decent option to me. I'm don't quite like system() and
>> global() as names yet, as they don't really make it clear that one of them
>> is deterministic. Other t
On Friday, 13 October 2017 01:30:57 PDT Lars Knoll wrote:
> This sounds like a decent option to me. I'm don't quite like system() and
> global() as names yet, as they don't really make it clear that one of them
> is deterministic. Other than that this looks like a good way forward.
Well, one of th
> On 12 Oct 2017, at 17:11, Thiago Macieira wrote:
>
> On quinta-feira, 12 de outubro de 2017 01:28:34 PDT Edward Welbourne wrote:
>>> So I created a better option: QPseudoRandomGenerator (name bikeshedding
>>> later)
>> I should note that "pseudo-random" is in fact a variant on "chaotic", so
>>
On Thursday, 12 October 2017 10:58:25 PDT Thiago Macieira wrote:
> Oops, if I mask off then I need to change the number I'm dividing by. New
> implementation:
>
> static double generateDouble()
> {
> // use generate64() to get enough bits
> quint64 x = generate64();
> quint64 limit = Q
On quinta-feira, 12 de outubro de 2017 10:42:53 PDT Thiago Macieira wrote:
> Yet my code is not optimal, since it generates a check for the sign bit
> because the x86 instruction CVTSI2SD takes a signed integer as input. That's
> useless, since the result has only 53 bits of randomness anyway. So a
On quinta-feira, 12 de outubro de 2017 10:06:05 PDT Thiago Macieira wrote:
> The conversion to double via ldexp is what generateDouble() does in the new
> class and is optional. Though I will take a look now to see if using ldexp()
> produces better code than
>
> return double(generate64()) / (dou
On 2017-10-12 13:06, Thiago Macieira wrote:
> libstdc++'s LCG does:
> _M_x = __detail::__mod<_UIntType, __m, __a, __c>(_M_x);
> return _M_x;
>
> which is
>
> _M_x = (__a * _M_x + __c) % __m;
...and yet, for some reason when I tested it, it was *quite* slow.
Noticeably slower than MT
On quinta-feira, 12 de outubro de 2017 09:23:13 PDT Matthew Woehlke wrote:
> The last time I found myself in need of a graphic/game quality PRNG, I
> tried fiddling with both rand48 (POSIX) and C++11 MT, and ended up using
> this instead:
>
> m_seed = ( ( 19073486328125 * m_seed ) + 1 ) & 0x7
On 2017-10-11 12:12, Thiago Macieira wrote:
> I created a better option: QPseudoRandomGenerator (name bikeshedding later)
> on the flight home from QtCS. It's a simple wrapper around the Mersenne
> Twister
> provided by the Standard C++ Library
The last time I found myself in need of a graphic/
On quinta-feira, 12 de outubro de 2017 01:28:34 PDT Edward Welbourne wrote:
> > So I created a better option: QPseudoRandomGenerator (name bikeshedding
> > later)
> I should note that "pseudo-random" is in fact a variant on "chaotic", so
> perhaps QChaoticGenerator would be more apt. Chaos is not
Thiago Macieira (11 October 2017 18:12)
> I've come to the conclusion that adding QRandomGenerator, a (mostly)
> cryptogrphically-secure PRNG, without adding a corresponding deterministic
> PRNG is a bad idea, especially with the changes that went in to the examples
> that changed all uses of qrand
Hello
I've come to the conclusion that adding QRandomGenerator, a (mostly)
cryptogrphically-secure PRNG, without adding a corresponding deterministic
PRNG is a bad idea, especially with the changes that went in to the examples
that changed all uses of qrand() to QRandomGenerator. We're telling
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