[Bug c/36869] New: OpenMP issue in gcc vs icc

["kemalihsan dot 1 at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

Hello all,

I guess there is something wrong with gcc 4.3.1 + openmp. Here how it went 
with me

Well on this page :
http://www.kallipolis.com/openmp/1.html

I tried taylor.c and taylor_mp.c
compiler options as follows:

gcc -O3 taylor.c -o taylor_gcc
icc -O3 taylor.c -o taylor_icc
gcc -O3 -fopenmp taylor_mp.c -o taylor_mp_gcc
icc -O3 -openmp taylor_mp.c -o taylor_mp_icc

Results summarized:
Only gcc + openmp gave different result, which was wrong according to the web
page. Of course there was no speedup. Reason might be due to the number of
steps. Being low, so that synchronization of threads was costly.



taylor_gcc :
Values: e*pi = 8.539734
Total elapsed time: 5500.000 seconds


taylor_icc :
Values: e*pi = 8.539734
Total elapsed time: 2920.000 seconds

** taylor_mp_gcc:
** Values: e*pi = 8.940247
** Total elapsed time: 8170.000 seconds

taylor_mp_icc:
Values: e*pi = 8.539734
Total elapsed time: 6020.000 seconds


My system summary :

OS : OpenSUSE 11.0 Linux 64 bit + kernel 2.6.25.9-0.2-default

gcc version : gcc (SUSE Linux) 4.3.1 20080507 (prerelease) [gcc-4_3-branch
revision 135036]

CPU : Intel quad core Q6600 (G0 stepping) on ASUS P5K SE

icc version : icc (ICC) 10.1 20080312


Let me know if you need more detail.


God bless your work!

PS: I saw this bug(!) on another web page too!!!

Kemal Kilic

kemalihsan.1@gmail.com


-- 
           Summary: OpenMP issue in gcc vs icc
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kemalihsan dot 1 at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36869