Re: Compute Unique Numbers in a Set

From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.lang.c++
Subject	Re: Compute Unique Numbers in a Set
Date	2023-01-17 17:32 +0000
Organization	A noiseless patient Spider
Message-ID	<878ri12hjh.fsf@bsb.me.uk> (permalink)
References	(16 earlier) <tq5ln0$35a9d$1@dont-email.me> <tq5prq$1u45$1@gioia.aioe.org> <tq66tg$38bg3$1@dont-email.me> <3d614abf-c869-4288-8837-2a7e9c11050bn@googlegroups.com> <tq6i65$b6g$1@gioia.aioe.org>

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Muttley@dastardlyhq.com writes:

> On Tue, 17 Jan 2023 07:48:02 -0800 (PST)
> Malcolm McLean <malcolm.arthur.mclean@gmail.com> wrote:
>>On Tuesday, 17 January 2023 at 13:13:37 UTC, Bonita Montero wrote:
>>> 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
>
> Just out of interest, what would be a better way?

"Better" depends on the context.  This thread has been split between
comp.lang.c and comp.lang.c++ and if you have not been reading both you
won't have seen all the many proposed algorithms.  There are lots of
possible trade-offs between the number of random number call, the amount
of storage needed and sizes of the numbers involved.

It isn't even clear what's wanted.  The OP might have wanted just a
random selection (all possible subsets equally probable) they might have
wanted a random permutation (where all possible sequences of all
possible subsets are equally probable).

-- 
Ben.

Thread

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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