AVX is slower than serial execution ?

I write a simple program and build with icpc to examine the performance of AVX in my mathine. The code snippet is as following,

  #define T 2000000
  #define X 16
  #define Y 16
  #define Z 16

  for(int t=0;t<T;t++)
  for(int k=0;k<Z;k++)
  for(int j=0;j<Y;j++)
  for(int i=0;i<X;i++)
    A[k][j][i]=B[k][j][i]+C[k][j][i];

The configures are as following,

            icpc version 13.1.0 (gcc version 4.6.1 compatibility)

            FFLAGS="-O3 -xhost "

            Intel(R) Xeon(R) CPU E5-2670 0 @ 2.60GHz

            Red Hat Enterprise Linux Server release 6.3 (Santiago)

The exeperiment result is as following,

collapse;width:216pt" width="288">
niterator 2000000 2000000 200000 size 12*12*12 16*16*16 32*32*32 time  (s) 　 　 　 serial 1.09918 2.58384 2.99971 avx 1.71405 4.01935 5.18318

 As the table, AVX version always cost more time then serial version.

Can somebody know why?

Thanks in advance!!!