-openmp flag slowing down my code...

-openmp flag slowing down my code...

Id like to know why the serial version of my program, compiled without -openmp flag, runs faster than the parallel version compiled with -openmp and ran in serial mode with OMP_NUM_THREADS=1?

Details:

CPU Itanium 2 1.3Ghz 3mb L3 cache
Red Hat Linux kernel 2.4.21-9.EL
Fortran Compiler for Itanium-based applications
Version 8.1 Build 20040802 Package ID: l_fc_p_8.1.018

------------------------------------
WITH OPENMP
FFLAGS= -c -tpp2 -O3 -fpp -openmp
LFLAGS= -openmp
export OMP_NUM_THREADS=1
The program ran in 167 seconds

-------------------------------------
WITHOUT OPENMP
FFLAGS= -c -tpp2 -O3 -fpp
LFLAGS=
The program ran in 73 seconds

...

PS.: In attach follow my main parallel routine.

Thanks in advance

Renato N. Elias
COPPE/UFRJ
Rio de Janeiro/Brasil
http://www.nacad.ufrj.br/~rnelias

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