cstdatomic (c++0x std::atomic) / g++ 4.4
Posted on
16th Feb 2014 07:03 pm by
admin
Hello,
I'm trying to use cstdatomic (std::atomic in the upcoming c++0x standard) in g++ 4.4, but it doesn't seems to work as expected and I would like to known if I missed something...
Did you know?Explore Trending and Topic pages for more stories like this.
My goal in the code below is just to test differents ways of concurrency (mutex vs atomic) : 4 threads increments counters in 3 ways.
1 - with std::mutex : works perfectly but slightly slow (lock / unlock)
2 - with g++ atomics "builtins" : works perfectly
3 - with std::atomic : doesn't works.
here is the code :
#include
#include
#include
int cnt_mutex = 0;
int cnt_builtins = 0;
std::atomic cnt_stdatomic = {0};
std::mutex smutex;
/* thread code */
void thrcode(int thrid)
{
/* counter local to thread */
int cnt_local;
for (cnt_local = 0; cnt_local < 10000000; cnt_local++)
{
/* c++0x fetchadd -> FAIL */
cnt_stdatomic.fetch_add(1);
/* g++ builtin fetchadd -> OK */
__sync_fetch_and_add(&cnt_builtins,1);
/* scoped std::mutex : OK */
{
std::unique_lock lockit(smutex);
cnt_mutex++;
};
};
printf("thread(%d) : cnt_local %dn",thrid,cnt_local);
};
int main() {
/* thread init */
std::thread m1(thrcode,1),m2(thrcode,2),m3(thrcode,3),m4(thrcode,4);
/* wait all thread */
m1.join(); m2.join(); m3.join(); m4.join();
/* display counters */
printf("end : cnt_mutex %d, cnt_builtins %d, cnt_stdatomic %dn",
cnt_mutex,cnt_builtins,(int)cnt_stdatomic);
};
compile with : g++ -std=c++0x mt.cpp -O3 -pthread && date && ./a.out && date
it give :
dimanche 4 octobre 2009, 19:10:28 (UTC+0200) (french time...)
thread(1) : cnt_local 10000000
thread(3) : cnt_local 10000000
thread(4) : cnt_local 10000000
thread(2) : cnt_local 10000000
end : cnt_mutex 40000000, cnt_builtins 40000000, cnt_stdatomic 39990400
dimanche 4 octobre 2009, 19:10:46 (UTC+0200)
cnt_stdatomic counter is incorrect... Someone could tell me where i'm wrong, did i miss something in code ?
(I'm using g++ version 4.4.1 Ubuntu 4.4.1-4ubuntu6)
Thanks !
No comments posted yet
Your Answer:
Login to answer
268 
14 
Other forums
NOOB needs help with upload file
The intent of this form is to create a folder for a client and upload an image into another folder '
limit string by words??
hello all,
I was wonder if there is a function to limit a string by the number of words inste
using file_get_contents??
okay how would i create a script using file_get_contents() in php have it grab search pages 1-20 and
Echo Tweaking help!
HI. I would like to have the output of the entered variables repeat forever, but it's stopping at th
RSS feed - FeedList for WordPress
Hi,
I'm trying to alter the FeedList plugin for WordPress so that I can click on the title of
rookie looking for help coding a CSS form with PHP
I'm trying to figure out how to add PHP code to my xhtml form so that it is a working form embedded
article site help remaining text
Hi all hope you will be fine
I am creating a article site in this site i want to put some text on
first few characters only
hi, does anyone know how to use PHP to take the first few words of a text and limit them? i have see
SAP Project Module
I have seen in the SAP Project Module,plan cost and budget are not equal and even difference is sign
Save data in input fields when they press "BACK BUTTON"
Hi, this is html form: And let's say they get a error "Please enter ur title must be more then
