I doing some test on multicore processor using MKL library. For that reason, I am testing DGEQRF routine of MKL library it is a very small program. My problem is that when I use one openmp
one thread I get time
real 3m36.934s
user 3m30.713s
sys 0m2.300s
when using 2 threads
real 0m27.402s
user 0m42.727s
sys 0m1.032s
ratio is approx 7 times higher while it should be approx 2 times. Please someone could explain me this?
compiling option%
gcc-4.2 -I/opt/intel/mkl/10.0.4.023/include/ -fPIC text.c -fopenmp -L/opt/intel/mkl/10.0.4.023/lib/32 -lmkl_gf -liomp5 /opt/intel/mkl/10.0.4.023/lib/32/libmkl_lapack.a /opt/intel/mkl/10.0.4.023/lib/32/libmkl_gnu_thread.a /opt/intel/mkl/10.0.4.023/lib/32/libmkl_cdft_core.a -ldl -lm
program file%
#include
#include
#include
#include
int main(int argc, char *argv[])
{
int M, N,j,LWORK,info;
double *val,*tau,*work;
M=200000;
N=500;
val = malloc(M*N*sizeof(double));
tau = malloc(M*sizeof(double));
work = malloc(M*sizeof(double));
for (j=0; j val=floor(100*( ( (double)rand()*2.0/RAND_MAX )-1.0 ) );
}
LWORK=N;
dgeqrf_(&M,&N,val,&M,tau,work,&LWORK,&info);
}
thanks a lot
Alok
