I just write the following code:
--------------------------------
int main() {
int i = 0;
int s = 0;
#pragma omp parallel for
for(i = 0; i < 10001; i++) {
/* uncommenting the follow line, it works */
printf("thread %d : %d\n", omp_get_thread_num(), s = s + i);
/* uncommenting the follow line, it gets wrong */
/* s += i; */
/* but when uncommenting the follow line, the above line works
*/
/* printf("%d\n", s); */
}
printf("%d\n", s);
}
------------------------------------------------
The above runs just as I described in the comment.
when I said "it gets worng", I mean that, when I run it many time, it returns
different result, but every one is wrong.
such as:
----------------------------------------
$ ./another
31653559
lfs_625:wizard | Sat 12 Apr 2008 11:46:05 AM GMT | ~/programe/c/openMP
$ ./another
50005000
lfs_625:wizard | Sat 12 Apr 2008 11:46:06 AM GMT | ~/programe/c/openMP
$ ./another
24946634
lfs_625:wizard | Sat 12 Apr 2008 11:46:07 AM GMT | ~/programe/c/openMP
$ ./another
19633725
lfs_625:wizard | Sat 12 Apr 2008 11:46:07 AM GMT | ~/programe/c/openMP
$ ./another
49257506
lfs_625:wizard | Sat 12 Apr 2008 11:46:08 AM GMT | ~/programe/c/openMP
----------------------------------------
--
Summary: "omp parallel for" wrong result
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgomp
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: whitelilis at gmail dot com
GCC host triplet: "omp parallel for" gets the wrong result
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35912
