Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.c++ > #80039
| From | David Brown <david.brown@hesbynett.no> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: Have you ever noticed ... |
| Date | 2021-06-01 11:54 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <s95047$4dm$1@dont-email.me> (permalink) |
| References | <s94f96$3pv$1@dont-email.me> <s94mij$1l4$2@gioia.aioe.org> <s94t9r$iin$1@dont-email.me> |
On 01/06/2021 11:06, Bonita Montero wrote: >>> If you call ... >>> C:\Program Files (x86)\Microsoft Visual >>> Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat >>> ... and then ... >>> clang --version >>> ... then you get the nearly most recent clang (V11) with MSVC ? >>> But unfortunately for most benchmarks I wrote MSVC generates >>> better code than clang. > >> What optimization flags did you use? > > -O3 > There are also benchmarks which run faster with clang, > but most run faster with cl. -O3 is sometimes faster than -O2, and often slower. Don't use -O3 unless you know what you are doing, and have tested it to see that it is helpful for your particular requirements. (The same applies to gcc, to a slightly lesser extent.) clang also has a tendency to be enthusiastic about vectorisation and loop unrolling that can help for big data sets, but be noticeably bigger and slower on small sets. You see that especially on -O3, but also on -O2. Optimising is not just a matter of "bigger number means faster for all tests". (That said, MSVC can be quite efficient for some kinds of code - it's entirely possible that it is simply better for the examples you were using.)
Back to comp.lang.c++ | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Have you ever noticed ... Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-01 07:06 +0200
Re: Have you ever noticed ... Juha Nieminen <nospam@thanks.invalid> - 2021-06-01 07:11 +0000
Re: Have you ever noticed ... Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-01 11:06 +0200
Re: Have you ever noticed ... David Brown <david.brown@hesbynett.no> - 2021-06-01 11:54 +0200
Re: Have you ever noticed ... Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-01 12:25 +0200
Re: Have you ever noticed ... Bonita Montero <Bonita.Montero@gmail.com> - 2021-06-02 04:51 +0200
Re: Have you ever noticed ... Doctor Who <doc@tardis.org> - 2021-06-02 05:12 +0200
Re: Have you ever noticed ... doctor@doctor.nl2k.ab.ca (The Doctor) - 2021-06-02 04:10 +0000
Re: Have you ever noticed ... Michael S <already5chosen@yahoo.com> - 2021-06-01 13:23 -0700
Re: Have you ever noticed ... Real Troll <real.troll@trolls.com> - 2021-06-01 22:47 +0100
Re: Have you ever noticed ... Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-01 18:24 -0700
Re: Have you ever noticed ... Michael S <already5chosen@yahoo.com> - 2021-06-02 14:02 -0700
Re: Have you ever noticed ... Juha Nieminen <nospam@thanks.invalid> - 2021-06-02 05:07 +0000
Re: Have you ever noticed ... Vir Campestris <vir.campestris@invalid.invalid> - 2021-06-06 21:30 +0100
csiph-web