Friday, July 21, 2023

Digest for comp.lang.c++@googlegroups.com - 7 updates in 4 topics

Bonita Montero <Bonita.Montero@gmail.com>: Jul 21 04:51AM +0200

Am 20.07.2023 um 21:57 schrieb Chris M. Thomasson:
 
>> For me is #define-ing NOMIMMAX before including <Windows.h>
>> the smarter solution.
 
> Don't forget  WIN32_LEAN_AND_MEAN ... :^)
 
That's 100ms difference when compiling for me (7950X).
Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo>: Jul 20 11:20PM -0400

Alf P. Steinbach wrote:
> Visual C++ and g++.
 
> Not what you're asking but note that
 
> * `typedef` is old C syntax, modern `using` can be more clear.
Any code is written to be read by humans. Uniform hurts the readability,
specific improves it. Plus, using declaration make the reader read more
tokens. Upshot: use typedef where you can and using where you can't.
 
> * `const` at namespace scope implies `static`, i.e. no need to repeat.
Another change from more to less readable code. In order to know a
declaration is in a namespace, one has to either keep this in mind or
look up. The former is inefficient in space, the latter -- in time.
Upshot: feel free to be helpful and use static.
 
Morale: a new shiny multitool is not a universally good replacement for
the old good pliers.
 
>         using ssize_t_2   = array_of_2_<ssize_t> ;
>     } // namespace fem
 
> - Alf
 
Cheers,
-Pavel
"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Jul 21 12:59PM -0700

On 7/20/2023 7:51 PM, Bonita Montero wrote:
 
>> Don't forget  WIN32_LEAN_AND_MEAN ... :^)
 
> That's 100ms difference when compiling for me (7950X).
 
:^) Still, its something that was ingrained in my brain from long ago.
Bonita Montero <Bonita.Montero@gmail.com>: Jul 21 11:15AM +0200

Years ago I wrote a mutex that allows multiple read accesses
or exclusive write access. Instead, I use limited configurable
spinning. Each spinning interval has an x86 PAUSE instruction
to conserve power and not suffocate other threads on the core.
This got me wondering how long a PAUSE instruction takes on
different x86 CPUs. That's why I wrote a small test C++20
program that you can try out. Here it is:
 
#include <iostream>
#include <chrono>
#include <cstdint>
#include <utility>
#if defined(_MSC_VER)
#include <intrin.h>
#else
#include <x86intrin.h>
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