GPU time slower than CPU

Hi everyone

Can you explain to me my code about gpu time?.

why gpu time is slower than CPU time.

this is my code:

    tic
n = 4096;
m = 1000;
A1 = ones(1,m);
B1 = 2*ones(m,n);
C1 = sum(A1*B1);
% wait(gpu)
toc

    tic
n = 4096;
m = 1000;
A2 = ones(1,m);
B2 = 2*ones(m,n);
C2 = sum(sum(bsxfun(@times,A2',B2)));
% wait(gpu)
toc

tic
n = 4096;
m = 1000;
A3 = gpuArray(ones(1,m));
B3 = gpuArray(2*ones(m,n));
C3 = sum(A3*B3);
% CB = sum(bsxfun(@times,AB',BB));
% wait(gpu)
toc

Thank

[Joss Knight]

Can you double-check your code? Because you're not actually doing the same thing on the GPU. For instance, you do a matrix multiplication on the GPU that you don't do on the CPU. The results aren't even the same dimensions.