Re: Compute Unique Numbers in a Set

From	"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups	comp.lang.c, comp.lang.c++
Subject	Re: Compute Unique Numbers in a Set
Date	2023-01-08 15:18 -0800
Organization	A noiseless patient Spider
Message-ID	<tpfj09$3v65t$1@dont-email.me> (permalink)
References	(4 earlier) <tpdim3$3p3kb$1@dont-email.me> <tpel4n$ivd$1@gioia.aioe.org> <tpeurf$15ot$1@gioia.aioe.org> <slrntrmecl.o81.ike@sverige.sdf.org> <tpfimu$5ft$1@gioia.aioe.org>

Cross-posted to 2 groups.

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On 1/8/2023 3:13 PM, Bart wrote:
> On 08/01/2023 21:45, Ike Naar wrote:
>> On 2023-01-08, Bart <bc@freeuk.com> wrote:
>>> On 08/01/2023 14:48, Bart wrote:
>>>> On 08/01/2023 05:01, Bonita Montero wrote:
>>>>> Now it's perfect:
>>>>>
>>>>> <snip complicated C++ code>>
>>>
>>>> That's some torturous-looking code.
>>>
>>> I tested your [BM] code for speed, using N=1000000, and limits of 
>>> 1..N+1.
>>>
>>> The 'cout' in the loop was replaced with a count of all the values, so
>>> that at the end the total was displayed to be able to compare results.
>>>
>>> The C++ with gcc-O3 took 1.25 seconds.
>>>
>>> My script initially took much longer due to using an unordered list
>>> (storing up to 1M values). But I tweaked it use a bit-set.
>>>
>>> Then it took 0.67 seconds.
>>>
>>>
>>> (Revised script:)
>>>>   ??? a:=new(set,lower..upper)
>>>>       sum:=0
>>>
>>>>   ??? to n do
>>>>   ??????? repeat
>>>>   ??????????? x:=random(lower..upper)
>>>>   ??????? until x not in a
>>>>   ??????? a[x]:=1
>>>>           sum+:=x
>>>>   ??? od
>>
>> In the program below, each random number requires only constant time and
>> retries are not necessary.
>> For N=1000000 it runs in 0.01 second.
>>
>>
>> #include <stdlib.h>
>> #include <stdio.h>
>>
>> enum {N = 1000000};
>> static int used;
>> static int numbers[N];
>> /*
>>    numbers[0 .. N) contain a permutation of [0 .. N)
>>    0 <= used <= N
>>    numbers[0 .. used) are available
>>    numbers[used .. N) are already used
>> */
>>
>> static void reset(void)
>> {
>>    /* mark all numbers[0..N) as available */
>>    used = N;
>> }
>>
>> static void init(void)
>> {
>>    /* fill numbers[0..N) with a permutation of [0..N) */
>>    for (int i = 0; i != N; ++i)
>>    {
>>      numbers[i] = i;
>>    }
>> }
>>
>> static int getrandom(void)
>> {
>>    /* pick a random value from the available numbers, and update the 
>> numbers array */
>>    if (used == 0)
>>    {
>>      puts("ran out of available numbers");
>>      abort();
>>    }
>>    int index = rand() % used;
>>    --used;
>>    int value = numbers[index];
>>    numbers[index] = numbers[used];
>>    numbers[used] = value;
>>    return value;
>> }
>>
>> static void run(int length)
>> /*
>>    generate a run of 'length' unique numbers from the range [0..N)
>> */
>> {
>>    reset();
>>    long long sum = 0;
>>    for (int i = 0; i != length; ++i)
>>    {
>>      sum += getrandom();
>>    }
>>    printf("%lld\n", sum);
>> }
>>
>> int main(void)
>> {
>>    /* if necessary, seed the PRNG (not done here) */
>>    init();
>>    run(N);
>>    return 0;
>> }
> 
> So, this is more of a shuffle? Since the set of numbers is not really 
> random, it's a permutation of a consecutive range of values

[...]

It looks like shuffle of a set of unique numbers.

Thread

Compute Unique Numbers in a Set Albert <invalid@gmail.com> - 2022-12-26 23:45 +0000
  Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-26 16:52 -0800
    Re: Compute Unique Numbers in a Set tTh <tth@none.invalid> - 2022-12-27 02:44 +0100
      Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-27 13:35 -0800
  Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-26 20:47 -0500
    Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 15:57 +0000
      Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 11:16 -0500
        Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 16:59 +0000
          Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 12:24 -0500
            Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 17:53 +0000
              Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 13:50 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 20:08 +0000
                Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 15:31 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-28 02:57 +0000
                Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 23:02 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-29 02:06 +0000
                Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-28 23:42 -0500
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-29 12:26 +0000
  Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-27 07:34 -0800
  Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-27 16:18 +0000
    Re: Compute Unique Numbers in a Set Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2022-12-28 01:08 +0000
      Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-28 03:30 +0000
    Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-27 19:42 -0800
  Re: Compute Unique Numbers in a Set Manu Raju <MR@invalid.invalid> - 2022-12-27 18:11 +0000
  Re: Compute Unique Numbers in a Set antispam@math.uni.wroc.pl - 2022-12-28 01:32 +0000
    Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 21:13 -0500
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-27 19:48 -0800
        Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2022-12-27 23:06 -0500
      Re: Compute Unique Numbers in a Set antispam@math.uni.wroc.pl - 2022-12-29 19:47 +0000
  Re: Compute Unique Numbers in a Set jak <nospam@please.ty> - 2022-12-28 11:28 +0100
  Re: Compute Unique Numbers in a Set Rosario19 <Ros@invalid.invalid> - 2023-01-01 21:06 +0100
    Re: Compute Unique Numbers in a Set Rosario19 <Ros@invalid.invalid> - 2023-01-02 06:43 +0100
  Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-01 23:19 +0000
    Re: Compute Unique Numbers in a Set jak <nospam@please.ty> - 2023-01-02 07:28 +0100
      Re: Compute Unique Numbers in a Set jak <nospam@please.ty> - 2023-01-02 08:48 +0100
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-01 23:53 -0800
        Re: Compute Unique Numbers in a Set Öö Tiib <ootiib@hot.ee> - 2023-01-02 01:18 -0800
    Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-02 13:49 +0000
  Re: Compute Unique Numbers in a Set Bart <bc@freeuk.com> - 2023-01-02 12:27 +0000
  Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2023-01-02 12:13 -0500
    Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-02 17:31 +0000
      Re: Compute Unique Numbers in a Set Richard Damon <Richard@Damon-Family.org> - 2023-01-02 12:46 -0500
      Re: Compute Unique Numbers in a Set Siri Cruise <chine.bleu@yahoo.com> - 2023-01-02 18:54 -0800
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-02 20:52 -0800
      Re: Compute Unique Numbers in a Set David Brown <david.brown@hesbynett.no> - 2023-01-03 09:01 +0100
      Re: Compute Unique Numbers in a Set Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-03 07:28 -0800
        Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-03 15:46 +0000
          Re: Compute Unique Numbers in a Set David Brown <david.brown@hesbynett.no> - 2023-01-03 18:19 +0100
  Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 03:48 +0100
    Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 04:18 +0100
    Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-08 03:48 +0000
      Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 05:12 +0100
        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 Paavo Helde <eesnimi@osa.pri.ee> - 2023-01-08 21:19 +0200
          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 Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-09 14:48 -0800
              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> - 2023-01-09 18:28 -0800
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-09 18:44 -0800
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-10 03:08 +0000
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-09 19:19 -0800
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-10 17:30 +0000
                Re: Compute Unique Numbers in a Set Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-10 09:45 -0800
                Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-10 02:57 +0000
              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 Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-01-13 03:32 -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 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 tTh <tth@none.invalid> - 2023-01-08 10:13 +0100
          Re: Compute Unique Numbers in a Set Bonita Montero <Bonita.Montero@gmail.com> - 2023-01-08 10:25 +0100
            Re: Compute Unique Numbers in a Set gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-08 13:20 +0000
    Re: Compute Unique Numbers in a Set "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-08 13:09 -0800
  Re: Compute Unique Numbers in a Set Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-09 02:37 +0000
  Re: Compute Unique Numbers in a Set John Forkosh <forkosh@panix.com> - 2023-01-15 02:49 +0000

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