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Groups > comp.lang.c > #168703
| From | jak <nospam@please.ty> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Compute Unique Numbers in a Set |
| Date | 2023-01-02 07:28 +0100 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <totti7$6if$1@gioia.aioe.org> (permalink) |
| References | <todbqe$16sg$1@gioia.aioe.org> <tot4eh$21qv0$1@news.xmission.com> |
Il 02/01/2023 00:19, Kenny McCormack ha scritto:
> In article <todbqe$16sg$1@gioia.aioe.org>, Albert <invalid@gmail.com> wrote:
>> Is this the best way to generate unique random numbers in a set of 6
>> numbers?
>>
>>
>> <******************************************************>
>
> Here's my contribution to this thread.
>
> Note that this is both gcc- and Linux- specific, as well as being
> hard-coded to OP's problem specification. Note also that I took the
> liberty of assuming that OP actually, really, did want random numbers
> between 0 and 59; this would be suitable if, say, OP was looking for a
> random number of minutes or seconds (and we could be talking either about
> time intervals or about locations/distances expressed in terms of latitude
> and/or longitude).
>
> --- Cut Here ---
> #include <stdio.h>
> #include <stdint.h>
>
> int main(void)
> {
> uint64_t num = 0, j = 1;
> FILE *fp = fopen("/dev/urandom","r");
>
> while (__builtin_popcount(num) < 6)
> num |= 1 << (fgetc(fp) % 60);
>
> for (int i=0; i<60; i++, j *= 2)
> if (num & j)
> printf("i = %d, j = %ld\n",i,j);
> return 0;
> }
> --- Cut Here ---
>
> The values printed out of the variable "i" are your random numbers.
>
HI,
I state that I have not worried about the randomization algorithm chosen
by the OP and, so I focused on data storage.
Your storage method is similar to mine because both algorithms use a
lookup table with the difference that mine uses an array of characters
while your use the bits of an uint64_t. However I found a few Issues in
your source code:
The first concerns the use of the "__builtin_popcount" function, this
function does not work with uint64_t but with unsigned int.
#include <stdio.h>
#include <stdint.h>
int main()
{
uint64_t n = ~0;
printf ("value: %#lX bits: %d", n, __builtin_popcount(n));
return 0;
}
output: value: 0XFFFFFFFFFFFFFFFF bits: 32
This will have as a consequence that you will never get values greater
than 32.
The second issue concerns that your program will print the values
archived in numerical order and not in extraction order but perhaps this
does not affect the OP even if reading his code this seemed important.
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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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