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| Subject | Re: Count string in string with loop increase 2, why is this not faster? |
|---|---|
| Newsgroups | comp.lang.c |
| References | (15 earlier) <s9meC.917167$ch5.593863@fx18.am4> <2297ba4e-8d2f-4516-9907-b767f2836897@googlegroups.com> <aToeC.470372$oD1.406285@fx44.am4> <f510802b-1b52-465d-871d-c86e344feb89@googlegroups.com> <4410bfed-d828-477b-997e-be10f06391f4@googlegroups.com> |
| From | bartc <bc@freeuk.com> |
| Message-ID | <RwLeC.632366$9X.588558@fx09.am4> (permalink) |
| Organization | virginmedia.com |
| Date | 2018-02-07 22:59 +0000 |
On 07/02/2018 22:44, Bart Smissaert wrote:
> Sorry, that should be:
>
> SQLITE_API int sqlite3_CountCharInString(const wchar_t *strSearch, int nCount, const wchar_t *strChar)
> {
> int i;
> int total;
> total = 0;
>
> for (i = 0; i < nCount; i++)
> {
> //if (*strSearch == *strChar) total++;
> total = total + (*strSearch == *strChar);
Yeah, I already noticed!
This form avoids a conditional jump in the code, which presumably is
less efficient that always adding 0 or 1 to total on every character.
(I wrote the loop body as:
total += (*strSearch++ == strChar); // not *strchar
when I tested it. This reduced test time from 1.7 seconds to 1.2 seconds
(neither test using *strChar). However when using *strChar (ie. a
pointer to the find string character as you use), the faster timing was
only 1.3 seconds.
All tested with gcc -O0 to eliminate spurious timings.)
--
bartc
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Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 00:00 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-03 11:29 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 03:37 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-03 12:29 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 04:37 -0800
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-03 13:41 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 06:38 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-03 15:13 +0000
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-03 15:19 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 07:41 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-03 11:38 -0500
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-03 13:50 +0000
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-03 11:34 +0000
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-03 11:32 -0500
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-03 16:41 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 09:02 -0800
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 09:06 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-03 12:39 -0500
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-03 11:56 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-03 19:54 -0500
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-03 18:00 -0800
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-04 01:53 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 13:23 -0500
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-04 11:11 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 14:48 -0500
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-04 12:17 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-04 21:53 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-04 14:35 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-04 23:32 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-05 06:26 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-05 16:59 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-05 09:44 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-05 18:28 +0000
Re: Count string in string with loop increase 2, why is this not faster? scott@slp53.sl.home (Scott Lurndal) - 2018-02-05 18:41 +0000
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-05 20:08 +0000
Re: Count string in string with loop increase 2, why is this not faster? scott@slp53.sl.home (Scott Lurndal) - 2018-02-05 21:27 +0000
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-05 22:04 +0000
Re: Count string in string with loop increase 2, why is this not faster? scott@slp53.sl.home (Scott Lurndal) - 2018-02-05 22:38 +0000
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-06 01:34 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-06 06:39 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-06 18:07 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-06 12:34 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-06 21:12 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-06 13:42 -0800
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-06 16:43 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-07 01:10 +0000
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-06 18:47 -0800
Re: Count string in string with loop increase 2, why is this not faster? David Brown <david.brown@hesbynett.no> - 2018-02-07 15:13 +0100
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-07 14:48 +0000
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-07 17:13 +0000
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-07 17:27 +0000
Re: Count string in string with loop increase 2, why is this not faster? David Brown <david.brown@hesbynett.no> - 2018-02-07 17:01 +0100
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-07 02:00 -0800
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-07 12:02 +0000
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-07 14:46 +0000
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-07 13:56 +0000
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-07 11:17 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-06 23:59 -0800
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-07 05:10 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-07 11:01 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-07 14:24 -0800
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-07 14:44 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-07 22:59 +0000
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-07 15:20 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-07 23:31 +0000
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-07 15:32 -0800
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-07 16:05 -0800
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-05 15:29 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 17:41 -0500
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-04 23:11 +0000
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 23:45 -0500
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-04 15:11 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-04 23:37 +0000
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-04 18:08 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 23:12 -0500
Re: Count string in string with loop increase 2, why is this not faster? David Brown <david.brown@hesbynett.no> - 2018-02-05 13:08 +0100
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-05 08:24 -0500
Re: Count string in string with loop increase 2, why is this not faster? David Brown <david.brown@hesbynett.no> - 2018-02-05 14:39 +0100
Re: Count string in string with loop increase 2, why is this not faster? Robert Wessel <robertwessel2@yahoo.com> - 2018-02-05 10:37 -0600
Re: Count string in string with loop increase 2, why is this not faster? supercat@casperkitty.com - 2018-02-05 13:52 -0800
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-05 22:29 +0000
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-05 09:01 -0800
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-05 18:44 +0000
Re: Count string in string with loop increase 2, why is this not faster? David Brown <david.brown@hesbynett.no> - 2018-02-06 10:42 +0100
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-06 11:17 +0000
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-06 08:40 -0500
Re: Count string in string with loop increase 2, why is this not faster? bartc <bc@freeuk.com> - 2018-02-06 14:08 +0000
Re: Count string in string with loop increase 2, why is this not faster? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-06 14:42 +0000
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-06 12:35 -0800
Re: Count string in string with loop increase 2, why is this not faster? David Brown <david.brown@hesbynett.no> - 2018-02-06 23:04 +0100
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 17:35 -0500
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-04 14:38 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 17:57 -0500
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-04 15:22 -0800
Re: Count string in string with loop increase 2, why is this not faster? Bart Smissaert <bart.smissaert@gmail.com> - 2018-02-04 12:19 -0800
Re: Count string in string with loop increase 2, why is this not faster? Richard Damon <Richard@Damon-Family.org> - 2018-02-04 16:42 -0500
Re: Count string in string with loop increase 2, why is this not faster? Keith Thompson <kst-u@mib.org> - 2018-02-03 13:38 -0800
Re: Count string in string with loop increase 2, why is this not faster? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-02-03 22:03 +0000
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