CUDA GPU is slower than CPU

I find it hard to understand why my cuda code is slower than my processor code

my desktop configuration is i7 2600S, geforce 560ti

and my code is as follows:

int** kernel_shiftSeam(int **MCEnergyMat, int **newE, int *seam, int width, int height,     int direction)
{
//time measurement
float elapsed_time_ms = 0;
cudaEvent_t start, stop; //threads per block

dim3 threads(16,16);
//blocks
dim3 blocks((width+threads.x-1)/threads.x, (height+threads.y-1)/threads.y);

int *device_Seam;

int *host_Seam;

int seamSize;
if(direction == 1)
{
    seamSize = height*sizeof(int);
    host_Seam = (int*)malloc(seamSize);
    for(int i=0;i<height;i++)
    host_Seam[i] = seam[i];
}
else
{
    seamSize = width*sizeof(int);
    host_Seam = (int*)malloc(seamSize);
    for(int i=0;i<width;i++)
        host_Seam[i] = seam[i];
}

cudaMalloc((void**)&device_Seam, seamSize);
cudaMemcpy(device_Seam, host_Seam, seamSize, cudaMemcpyHostToDevice);

global_host_MC = MCEnergyMat;
new_host_MC = newE;

//copy host array to device
cudaMemcpy(global_MC, global_MC2, sizeof(int*)*width, cudaMemcpyHostToDevice);
    for(int i=0;i<width;i++)
        cudaMemcpy(global_MC2[i], global_host_MC[i], sizeof(int)*height, cudaMemcpyHostToDevice);

cudaMemcpy(new_MC, new_MC2, sizeof(int*)*width, cudaMemcpyHostToDevice);
    for(int i=0;i<width;i++)
        cudaMemcpy(new_MC2[i], new_host_MC[i], sizeof(int)*height, cudaMemcpyHostToDevice);


cudaEventCreate(&start);
cudaEventCreate(&stop);
cudaEventRecord(start, 0);

//do some operations on the 2d matrix
gpu_shiftSeam<<< blocks,threads >>>(global_MC, new_MC, device_Seam, width, height);

//measure end time for cpu calcuations
cudaEventRecord(stop, 0);
cudaEventSynchronize(stop);
cudaEventElapsedTime(&elapsed_time_ms, start, stop );

execTime += elapsed_time_ms;

//copy out the data back to host (RESULT)
for(int i=0;i<width;i++)
{
    cudaMemcpy(newE[i], new_MC2[i], sizeof(int)*height, cudaMemcpyDeviceToHost);
}

return newE;
}

I looped it 800 times and got the following results:

GPU Computing time (part of gpu_shiftseam): 1176 ms Total program execution time: 22 s

Processor Calculation time (same operation as gpu_shiftseam, but on the host): 12522ms Total program execution time: 12 s

-, , , - gpu , - ? - /, ? "" ?

!