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Groups > comp.lang.c > #147725
| From | Manfred <noname@add.invalid> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Bart, a tcc "issue" |
| Date | 2019-11-07 18:22 +0100 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <qq1jt6$1pu7$1@gioia.aioe.org> (permalink) |
| References | <uRIwF.17878$kE3.891@fx36.iad> |
On 11/7/2019 12:40 AM, DFS wrote:
> I wrote a distribution of characters counter, and on tcc (0.9.26) on
> Windows it always undercounts the last character in the set (9). If you
> have tcc on Windows maybe you could test it. Doesn't happen on
> gcc/MSYS2/Windows.
>
As Bart pointed out, this is not specific to tcc, but it is related to
the value of RAND_MAX instead.
The cause of this behavior is that you have a mistake in the randNbr
function: it does not map correctly the [0, RAND_MAX ] interval to [low,
high], in particular it does not map the last interval entirely, so you
get less counts on that interval because the distribution of rand() is
uniform.
>
> =====================================================================
> #include <stdlib.h>
> #include <stdio.h>
> #include <time.h>
> #include <math.h>
> #include <string.h>
#include <assert.h>
>
> int randNbr(int low, int high) {
// the following is not correct: it should be:
return low + (rand() * (long long)(high - low + 1)) / (RAND_MAX + 1);
> // return (low + rand() / (RAND_MAX / (high - low + 1) + 1));
> }
>
> int main(void) {
>
> int i=0,j=0,k=0,cnt=0;
>
> srand(time(NULL));
>
> char charset[63] =
> "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
> int charsetLen = strlen(charset);
> printf("n = 1000000\n");
> for(i=0;i<charsetLen;i++) {
> for(j=0;j<1000000;j++) {
> k = randNbr(0,charsetLen-1);
assert(charsetLen > k);
> if(charset[i] == charset[k]) {cnt++;}
> }
> printf("%c = %d\n",charset[i],cnt);
> cnt=0;
> }
> exit(0);
> }
>
> =====================================================================
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Bart, a tcc "issue" DFS <nospam@dfs.com> - 2019-11-06 18:40 -0500
Re: Bart, a tcc "issue" Bart <bc@freeuk.com> - 2019-11-07 00:03 +0000
Re: Bart, a tcc "issue" Bart <bc@freeuk.com> - 2019-11-07 00:06 +0000
Re: Bart, a tcc "issue" Bart <bc@freeuk.com> - 2019-11-07 01:44 +0000
Re: Bart, a tcc "issue" James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-11-07 10:05 -0500
Re: Bart, a tcc "issue" DFS <nospam@dfs.com> - 2019-11-07 13:22 -0500
Re: Bart, a tcc "issue" DFS <nospam@dfs.com> - 2019-11-08 09:19 -0500
Re: Bart, a tcc "issue" James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-11-08 11:03 -0500
Re: Bart, a tcc "issue" Manfred <noname@add.invalid> - 2019-11-07 18:22 +0100
Re: Bart, a tcc "issue" Manfred <noname@add.invalid> - 2019-11-07 18:30 +0100
Re: Bart, a tcc "issue" Richard Damon <Richard@Damon-Family.org> - 2019-11-08 20:51 -0500
Re: Bart, a tcc "issue" Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-08 20:59 -0800
Re: Bart, a tcc "issue" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-09 23:16 +0000
Re: Bart, a tcc "issue" Richard Damon <Richard@Damon-Family.org> - 2019-11-09 20:27 -0500
Re: Bart, a tcc "issue" Bart <bc@freeuk.com> - 2019-11-10 01:38 +0000
Re: Bart, a tcc "issue" Richard Damon <Richard@Damon-Family.org> - 2019-11-09 20:59 -0500
Re: Bart, a tcc "issue" Keith Thompson <kst-u@mib.org> - 2019-11-09 19:22 -0800
Re: Bart, a tcc "issue" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-10 03:04 +0000
Re: Bart, a tcc "issue" Richard Damon <Richard@Damon-Family.org> - 2019-11-09 23:04 -0500
Re: Bart, a tcc "issue" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-10 13:15 +0000
Re: Bart, a tcc "issue" Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-10 06:04 -0800
Re: Bart, a tcc "issue" Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-10 07:49 -0800
Re: Bart, a tcc "issue" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-10 17:49 +0000
Re: Bart, a tcc "issue" "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-11 02:44 -0800
Re: Bart, a tcc "issue" James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-11-11 13:57 -0500
Re: Bart, a tcc "issue" "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-14 16:51 -0800
Re: Bart, a tcc "issue" Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 16:03 -0800
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