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Re: Compute Unique Numbers in a Set

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  Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 06:01 +0100
    Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 14:48 +0000
      Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 18:22 +0100
        Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 17:46 +0000
          Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-09 04:58 +0100
            Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-09 11:26 +0000
              Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-09 15:57 +0100
      Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 17:34 +0000
        Re: Compute Unique Numbers in a Set Ike Naar <ike@sdf.org> - 2023-01-08 21:45 +0000
          Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-08 23:13 +0000
            Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-08 15:18 -0800
              Re: Compute Unique Numbers in a Set Tim Woodall <news001@woodall.me.uk> - 2023-01-13 06:35 +0000
                Re: Compute Unique Numbers in a Set Tim Woodall <news001@woodall.me.uk> - 2023-01-13 06:39 +0000
    Re: Compute Unique Numbers in a Set Paavo Helde <eesnimi@osa.pri.ee> - 2023-01-08 21:19 +0200
    Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-08 19:20 +0000
    Re: Compute Unique Numbers in a Set "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2023-01-09 12:03 +0100
      Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-09 17:42 +0100
        Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-09 23:22 +0000
        Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-10 05:11 -0800
          Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-10 05:19 -0800
        Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-13 08:26 +0100
          Re: Compute Unique Numbers in a Set Öö Tiib <ootiib@hot.ee> - 2023-01-13 03:26 -0800
          Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-13 12:21 +0000
            Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-13 14:11 +0100
              Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-13 13:55 +0000
                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-13 15:02 +0100
                  Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-13 14:17 +0000
          Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-15 16:06 +0100
            Re: Compute Unique Numbers in a Set Ralf Goertz <me@myprovider.invalid> - 2023-01-15 16:47 +0100
              Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-15 17:13 +0100
              Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-15 08:57 -0800
                Re: Compute Unique Numbers in a Set Ralf Goertz <me@myprovider.invalid> - 2023-01-16 09:46 +0100
                  Re: Compute Unique Numbers in a Set Ralf Goertz <me@myprovider.invalid> - 2023-01-16 10:21 +0100
                    Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-16 13:35 +0100
                      Re: Compute Unique Numbers in a Set Ralf Goertz <me@myprovider.invalid> - 2023-01-16 14:46 +0100
                      Re: Compute Unique Numbers in a Set Ralf Goertz <me@myprovider.invalid> - 2023-01-16 14:42 +0100
                        Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-16 16:38 +0000
                          Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-16 21:06 +0100
                            Re: Compute Unique Numbers in a Set Ralf Goertz <me@myprovider.invalid> - 2023-01-17 09:19 +0100
                              Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-17 09:30 +0000
                                Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-17 14:14 +0100
                                  Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-17 07:48 -0800
                                    Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-17 16:49 +0100
                                      Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-17 17:32 +0100
                                        Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-17 19:24 +0100
                                      Re: Compute Unique Numbers in a Set Ralf Goertz <me@myprovider.invalid> - 2023-01-17 17:31 +0100
                                        Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-17 17:10 +0000
                                          Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-17 18:18 +0100
                                            Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-18 09:23 +0000
                                              Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-18 13:31 +0100
                                                Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-18 16:16 +0000
                                                  Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-18 17:20 +0100
                                                    Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-18 16:24 +0000
                                                      Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-18 17:59 +0100
                                                        Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-18 17:14 +0000
                                                          Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-18 18:23 +0100
                                                            Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-19 09:31 +0000
                                      Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-17 12:48 -0800
                                        Re: Compute Unique Numbers in a Set scott@slp53.sl.home (Scott Lurndal) - 2023-01-17 21:21 +0000
                                          Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-17 13:29 -0800
                                            Re: Compute Unique Numbers in a Set Paul N <gw7rib@aol.com> - 2023-01-18 06:50 -0800
                                              Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-18 11:59 -0800
                                    Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-17 16:25 +0000
                                      Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-17 09:08 -0800
                                        Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-17 17:16 +0000
                                      Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-17 17:32 +0000
                                        Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-18 09:23 +0000
                                          Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-18 12:26 +0000
                                            Re: Compute Unique Numbers in a Set Muttley@dastardlyhq.com - 2023-01-18 16:09 +0000
            Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-15 16:27 +0000
              Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-15 17:42 +0100
            Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-15 17:11 +0000
    Re: Compute Unique Numbers in a Set Tim Woodall <news001@woodall.me.uk> - 2023-01-13 06:32 +0000
      Re: Compute Unique Numbers in a Set Öö Tiib <ootiib@hot.ee> - 2023-01-13 05:04 -0800

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#88555

Am 17.01.2023 um 10:30 schrieb Muttley@dastardlyhq.com:
> On Tue, 17 Jan 2023 09:19:44 +0100
> Ralf Goertz <me@myprovider.invalid> wrote:
>> Am Mon, 16 Jan 2023 21:06:41 +0100
>> schrieb Bonita Montero <Bonita.Montero@gmail.com>:
>>
>>> Am 16.01.2023 um 17:38 schrieb Muttley@dastardlyhq.com:
>>>
>>>> But wait, didn't she state that her algorithm was "perfect"? I
>>>> simply won't believe Bonita has more hubris and self delusion than
>>>> an angry mouse.
>>>
>>> And you don't check that Ralf's code does sth. completely different.
>>
>> I assume you don't mean to say, that I implemented your algorithm
>> incorrectly (if I'm wrong about that will you please care to elaborate?)
>> but that my algorithm is completely different from yours. Then, yes that
>> was my point. I don't understand why you use such a complicated
>> algorithm (compared to the very few lines I needed) if it doesn't
> 
> You must be new here :) Complexity is Bonitas calling card.

If you want the code to be as short and as performant
as possible there's no way to program different.

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#88560

On Tuesday, 17 January 2023 at 13:13:37 UTC, Bonita Montero wrote:
> Am 17.01.2023 um 10:30 schrieb Mut...@dastardlyhq.com: 
> > On Tue, 17 Jan 2023 09:19:44 +0100 
> > Ralf Goertz <m...@myprovider.invalid> wrote: 
> >> Am Mon, 16 Jan 2023 21:06:41 +0100 
> >> schrieb Bonita Montero <Bonita....@gmail.com>: 
> >> 
> >>> Am 16.01.2023 um 17:38 schrieb Mut...@dastardlyhq.com: 
> >>> 
> >>>> But wait, didn't she state that her algorithm was "perfect"? I 
> >>>> simply won't believe Bonita has more hubris and self delusion than 
> >>>> an angry mouse. 
> >>> 
> >>> And you don't check that Ralf's code does sth. completely different. 
> >> 
> >> I assume you don't mean to say, that I implemented your algorithm 
> >> incorrectly (if I'm wrong about that will you please care to elaborate?) 
> >> but that my algorithm is completely different from yours. Then, yes that 
> >> was my point. I don't understand why you use such a complicated 
> >> algorithm (compared to the very few lines I needed) if it doesn't 
> > 
> > You must be new here :) Complexity is Bonitas calling card.
> If you want the code to be as short and as performant 
> as possible there's no way to program different.
>
A shuffle followed by taking the first elements of the vector isn't a particularly
efficient way of generating a sequence of unique random numbers. But it's
not all that ineffieicnt either, and there's often an advantage in writing something
simply ans quickly from pre-existing components, rather than writing a tailor-
made, customised solution.

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#88561

Am 17.01.2023 um 16:48 schrieb Malcolm McLean:

> A shuffle followed by taking the first elements of the vector isn't a particularly
> efficient way of generating a sequence of unique random numbers. But it's
> not all that ineffieicnt either, and there's often an advantage in writing something
> simply ans quickly from pre-existing components, rather than writing a tailor-
> made, customised solution.

You don't have real randomness by shuffling.

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#88565

Am 17.01.2023 um 16:49 schrieb Bonita Montero:
> Am 17.01.2023 um 16:48 schrieb Malcolm McLean:
> 
>> A shuffle followed by taking the first elements of the vector isn't a 
>> particularly
>> efficient way of generating a sequence of unique random numbers. But it's
>> not all that ineffieicnt either, and there's often an advantage in 
>> writing something
>> simply ans quickly from pre-existing components, rather than writing a 
>> tailor-
>> made, customised solution.
> 
> You don't have real randomness by shuffling.

I found that you can randomly shuffle with random_shuffle or you provide
a shuffling function-object since C++17. That would be nice but if you
have a large number of values and chose only a small portion from that
this would take a lot of memory.

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#88573

Am 17.01.2023 um 17:32 schrieb Bonita Montero:

> I found that you can randomly shuffle with random_shuffle or you provide
> a shuffling function-object since C++17. That would be nice but if you
> have a large number of values and chose only a small portion from that
> this would take a lot of memory.
> 

I made a compromise between memory-consumption and performance. For
the following code if more than a tenth of the range is chosen for
the values I use a random-shuffle like operation. If less than a
tenth of the range is chosen I an unordered_set to check for col-
lisions. The decision is made depening on the PARTITIAL_THRESHOLD
variable.

#include <iostream>
#include <vector>
#include <charconv>
#include <random>
#include <concepts>
#include <unordered_set>

using namespace std;

int main( int argc, char **argv )
{
	try
	{
		if( argc < 4 ) [[unlikely]]
			return
				cout << argv[0] << " n from to" << endl,
				EXIT_FAILURE;
		auto parse = []( char const *str, char const *err )
		{
			size_t value;
			if( from_chars_result fcr = from_chars( str, str + strlen( str ), 
value ); (bool)fcr.ec || *fcr.ptr ) [[unlikely]]
				throw invalid_argument( err );
			return value;
		};
		size_t n = parse( argv[1], "wrong number of values" );
		if( !n ) [[unlikely]]
			return EXIT_SUCCESS;
		size_t
			from = parse( argv[2], "wrong from-value" ),
			to = parse( argv[3], "wrong to-value" );
		if( from > to ) [[unlikely]]
			swap( from, to );
		size_t range = to - from;
		if( n - 1 > range ) [[unlikely]]
			return
				cout << "n is too large" << endl,
				EXIT_FAILURE;
		vector<size_t> values;
		mt19937_64 mt;
		uniform_int_distribution<size_t> uidRange( 0, range );
		constexpr size_t PARTITIAL_THRESHOLD = 10;
		if( ++range && range / n >= PARTITIAL_THRESHOLD )
		{
			unordered_set<size_t> valuesSet;
			valuesSet.reserve( n );
			while( valuesSet.size() < n )
				for( ; ; )
					if( size_t value = uidRange( mt ); !valuesSet.contains( value ) )
					{
						valuesSet.emplace( value );
						break;
					}
			values.resize( n );
			auto itSetValue = valuesSet.cbegin();
			for( size_t i = 0; i != n; )
				values[i++] = *itSetValue++;
		}
		else
		{
			if( !range )
				throw bad_alloc();
			values.resize( range );
			for( size_t i = from; size_t &v : values )
				v = i++;
			for( size_t i = 0; i != n; )
				swap( values[i++], values[uidRange( mt )] );
			values.resize( n );
		}
		for( size_t i = 0; i != n; ++i )
			; //cout << values[i] << endl;
	}
	catch( exception const &exc )
	{
		return
			cout << exc.what() << endl,
			EXIT_FAILURE;
	}
}

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#88566

Am Tue, 17 Jan 2023 16:49:37 +0100
schrieb Bonita Montero <Bonita.Montero@gmail.com>:

> Am 17.01.2023 um 16:48 schrieb Malcolm McLean:
> 
> > A shuffle followed by taking the first elements of the vector isn't
> > a particularly efficient way of generating a sequence of unique
> > random numbers. But it's not all that ineffieicnt either, and
> > there's often an advantage in writing something simply ans quickly
> > from pre-existing components, rather than writing a tailor- made,
> > customised solution.  
> 
> You don't have real randomness by shuffling.

What makes you say that? Have a look at the first answer to that
question:
<https://cs.stackexchange.com/questions/47338/whats-a-uniform-shuffle>.
It shows that a properly implemented shuffle makes every permutation
equally probable. What more do you need for “real randomness”? While I
haven't checked the implementation of my c++ library
(libstdc++6-devel-gcc12-12.2.1+git537-1.2.x86_64) I have no doubt that
the authors have created a suitable one.

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#88568

On Tue, 17 Jan 2023 17:31:57 +0100
Ralf Goertz <me@myprovider.invalid> wrote:
>Am Tue, 17 Jan 2023 16:49:37 +0100
>schrieb Bonita Montero <Bonita.Montero@gmail.com>:
>
>> Am 17.01.2023 um 16:48 schrieb Malcolm McLean:
>>=20
>> > A shuffle followed by taking the first elements of the vector isn't
>> > a particularly efficient way of generating a sequence of unique
>> > random numbers. But it's not all that ineffieicnt either, and
>> > there's often an advantage in writing something simply ans quickly
>> > from pre-existing components, rather than writing a tailor- made,
>> > customised solution. =20
>>=20
>> You don't have real randomness by shuffling.
>
>What makes you say that? Have a look at the first answer to that
>question:
><https://cs.stackexchange.com/questions/47338/whats-a-uniform-shuffle>.
>It shows that a properly implemented shuffle makes every permutation
>equally probable. What more do you need for =E2=80=9Creal randomness=E2=80=
>=9D? While I
>haven't checked the implementation of my c++ library
>(libstdc++6-devel-gcc12-12.2.1+git537-1.2.x86_64) I have no doubt that
>the authors have created a suitable one.

To be pedantic, there's no real randomness at all if its simply generated
from a mathematical function because you only need to know the seed to 
reproduce the sequence. To be truly random you need a hardware source such as a
white noise generator. Even generators based on whats going on in the OS from 
users, network input etc isn't truly random and can be biased.

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#88570

Am 17.01.2023 um 18:10 schrieb Muttley@dastardlyhq.com:

> To be pedantic, there's no real randomness at all if its simply generated
> from a mathematical function because you only need to know the seed to
> reproduce the sequence. To be truly random you need a hardware source
> such as a white noise generator. Even generators based on whats going
> on in the OS from users, network input etc isn't truly random and can
> be biased.

You can initialize mt19937_64( (random_device())() ).
That's enough randomness for this task.

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#88594

On Tue, 17 Jan 2023 18:18:25 +0100
Bonita Montero <Bonita.Montero@gmail.com> wrote:
>Am 17.01.2023 um 18:10 schrieb Muttley@dastardlyhq.com:
>
>> To be pedantic, there's no real randomness at all if its simply generated
>> from a mathematical function because you only need to know the seed to
>> reproduce the sequence. To be truly random you need a hardware source
>> such as a white noise generator. Even generators based on whats going
>> on in the OS from users, network input etc isn't truly random and can
>> be biased.
>
>You can initialize mt19937_64( (random_device())() ).
>That's enough randomness for this task.

So is random() then. 

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#88598

Am 18.01.2023 um 10:23 schrieb Muttley@dastardlyhq.com:

> On Tue, 17 Jan 2023 18:18:25 +0100

> Bonita Montero <Bonita.Montero@gmail.com> wrote:

>> Am 17.01.2023 um 18:10 schrieb Muttley@dastardlyhq.com:

>> You can initialize mt19937_64( (random_device())() ).
>> That's enough randomness for this task.

> So is random() then.

Of course not. Mersenne Twister is the best of all non-cryptogra-
phical random number generators. It calculates a number of results
as a whole block for the next value-requests and thereby gets's a
unbeaten performance for this degree of randomness (mt19937_64 has
a period of of 2 ^ 19937 !). It's designed in a way that genrating
that block can easily optimized with vectoring instruction sets
like SSE or AVX.

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#88604

On Wed, 18 Jan 2023 13:31:23 +0100
Bonita Montero <Bonita.Montero@gmail.com> wrote:
>Am 18.01.2023 um 10:23 schrieb Muttley@dastardlyhq.com:
>
>> On Tue, 17 Jan 2023 18:18:25 +0100
>
>> Bonita Montero <Bonita.Montero@gmail.com> wrote:
>
>>> Am 17.01.2023 um 18:10 schrieb Muttley@dastardlyhq.com:
>
>>> You can initialize mt19937_64( (random_device())() ).
>>> That's enough randomness for this task.
>
>> So is random() then.
>
>Of course not. Mersenne Twister is the best of all non-cryptogra-
>phical random number generators. It calculates a number of results
>as a whole block for the next value-requests and thereby gets's a
>unbeaten performance for this degree of randomness (mt19937_64 has
>a period of of 2 ^ 19937 !). It's designed in a way that genrating
>that block can easily optimized with vectoring instruction sets
>like SSE or AVX.

I'll say again - there is no such thing as random for formula generated
"random" number sequences. Given the same start conditions the same sequence
will be generated whether its 2^19937 or 2^infinity. You'd be better off using
/dev/random, at least its entropy comes from nominally external sources so
is unpredictable in a busy enviroment.

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#88605

Am 18.01.2023 um 17:16 schrieb Muttley@dastardlyhq.com:

> I'll say again - there is no such thing as random for formula generated
> "random" number sequences. ...

I was talking about a non-cryptographical PRNG, and you talk about sth.
different because you have a constant feeling of uncertainty and you
think nothing is reliable in that sense.

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#88606

On Wed, 18 Jan 2023 17:20:23 +0100
Bonita Montero <Bonita.Montero@gmail.com> wrote:
>Am 18.01.2023 um 17:16 schrieb Muttley@dastardlyhq.com:
>
>> I'll say again - there is no such thing as random for formula generated
>> "random" number sequences. ...
>
>I was talking about a non-cryptographical PRNG, and you talk about sth.
>different because you have a constant feeling of uncertainty and you
>think nothing is reliable in that sense.

Pop psychology now? Really? Stick to writing over complicated code then 
bragging about how perfect it is so someone else can prove you wrong. Again.

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#88607

Am 18.01.2023 um 17:24 schrieb Muttley@dastardlyhq.com:

> Pop psychology now? Really? Stick to writing over complicated code then
> bragging about how perfect it is so someone else can prove you wrong. Again.

No one uses this perfect randomness you suggest but only as a seed for
a cryptographic PRNG. And for the purpose here you even don't need this
quality of randomness. Your personal issues aren't practically relevant.

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#88608

On Wed, 18 Jan 2023 17:59:08 +0100
Bonita Montero <Bonita.Montero@gmail.com> wrote:
>Am 18.01.2023 um 17:24 schrieb Muttley@dastardlyhq.com:
>
>> Pop psychology now? Really? Stick to writing over complicated code then
>> bragging about how perfect it is so someone else can prove you wrong. Again.
>
>No one uses this perfect randomness you suggest but only as a seed for
>a cryptographic PRNG. And for the purpose here you even don't need this

I was simply making a point that if you don't care about actual randomness
then standard RPGs are fine.

>quality of randomness. Your personal issues aren't practically relevant.

I'm not the one with the issues in this discussion.

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#88609

Am 18.01.2023 um 18:14 schrieb Muttley@dastardlyhq.com:

> I was simply making a point that if you don't care about actual randomness
> then standard RPGs are fine.

With that ?

| I'll say again - there is no such thing as random for formula generated
| "random" number sequences. Given the same start conditions the same 
sequence
| will be generated whether its 2^19937 or 2^infinity. You'd be better 
off using
| /dev/random, at least its entropy comes from nominally external sources so
| is unpredictable in a busy enviroment.

Absolutely not.

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#88620

On Wed, 18 Jan 2023 18:23:55 +0100
Bonita Montero <Bonita.Montero@gmail.com> wrote:
>Am 18.01.2023 um 18:14 schrieb Muttley@dastardlyhq.com:
>
>> I was simply making a point that if you don't care about actual randomness
>> then standard RPGs are fine.
>
>With that ?
>
>| I'll say again - there is no such thing as random for formula generated
>| "random" number sequences. Given the same start conditions the same 
>sequence
>| will be generated whether its 2^19937 or 2^infinity. You'd be better 
>off using
>| /dev/random, at least its entropy comes from nominally external sources so
>| is unpredictable in a busy enviroment.
>
>Absolutely not.

Really? How would go about predicting what packets will arrive on the network
or when a user will press a key then?

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#88575

On 1/17/2023 7:49 AM, Bonita Montero wrote:
> Am 17.01.2023 um 16:48 schrieb Malcolm McLean:
> 
>> A shuffle followed by taking the first elements of the vector isn't a 
>> particularly
>> efficient way of generating a sequence of unique random numbers. But it's
>> not all that ineffieicnt either, and there's often an advantage in 
>> writing something
>> simply ans quickly from pre-existing components, rather than writing a 
>> tailor-
>> made, customised solution.
> 
> You don't have real randomness by shuffling.
> 

Are you saying that there is no real randomness wrt shuffling a deck of 
cards around seven times in a row?

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#88576

"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> writes:
>On 1/17/2023 7:49 AM, Bonita Montero wrote:
>> Am 17.01.2023 um 16:48 schrieb Malcolm McLean:
>> 
>>> A shuffle followed by taking the first elements of the vector isn't a 
>>> particularly
>>> efficient way of generating a sequence of unique random numbers. But it's
>>> not all that ineffieicnt either, and there's often an advantage in 
>>> writing something
>>> simply ans quickly from pre-existing components, rather than writing a 
>>> tailor-
>>> made, customised solution.
>> 
>> You don't have real randomness by shuffling.
>> 
>
>Are you saying that there is no real randomness wrt shuffling a deck of 
>cards around seven times in a row?

That depends on how it is shuffled.

https://en.wikipedia.org/wiki/Faro_shuffle

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#88577

On 1/17/2023 1:21 PM, Scott Lurndal wrote:
> "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> writes:
>> On 1/17/2023 7:49 AM, Bonita Montero wrote:
>>> Am 17.01.2023 um 16:48 schrieb Malcolm McLean:
>>>
>>>> A shuffle followed by taking the first elements of the vector isn't a
>>>> particularly
>>>> efficient way of generating a sequence of unique random numbers. But it's
>>>> not all that ineffieicnt either, and there's often an advantage in
>>>> writing something
>>>> simply ans quickly from pre-existing components, rather than writing a
>>>> tailor-
>>>> made, customised solution.
>>>
>>> You don't have real randomness by shuffling.
>>>
>>
>> Are you saying that there is no real randomness wrt shuffling a deck of
>> cards around seven times in a row?
> 
> That depends on how it is shuffled.
> 
> https://en.wikipedia.org/wiki/Faro_shuffle

Touche. How about riffle shuffles?

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