http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
--- Comment #9 from FH fh_p at hotmail dot com 2012-05-12 21:27:31 UTC ---
Well...
I tested an OpenMP benchmarch (design to demonstrate OpenMP performances) found
on the web : multi-threaded (OpenMP) is again slower than single-threaded. I
looked
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
Bug #: 53292
Summary: multi-threaded (OpenMP) is slower than single-threaded
Classification: Unclassified
Product: gcc
Version: 4.6.2
Status: UNCONFIRMED
Severity: normal
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
--- Comment #1 from FH fh_p at hotmail dot com 2012-05-09 09:17:29 UTC ---
I am not sure to know if this problem is related rather to gcc or rather to
Ubuntu. I started with the assumption that is should rather to related to
gcc.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
--- Comment #2 from FH fh_p at hotmail dot com 2012-05-09 10:16:52 UTC ---
I have just tested on another computer (CPU : Xeon5650 12 cores + OS :
Scientific Linux) = I reproduce the unexpected behavior (OpenMP slower than
single-threaded).
So, I
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
--- Comment #4 from FH fh_p at hotmail dot com 2012-05-09 12:53:46 UTC ---
I don't understand your answer.
Timing just times the for loop. Checking array content is single threaded :
this is added to make sure the for loop has done the job
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
FH fh_p at hotmail dot com changed:
What|Removed |Added
Status|RESOLVED|UNCONFIRMED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
--- Comment #7 from FH fh_p at hotmail dot com 2012-05-09 14:36:00 UTC ---
Well...
Still don't really get why it is not possible to improve performance for such
basic things. I tried with allocations up to 7 Gb or more (RAM full + SWAP
full) : I
