Response of a system using DFT
It will match for circular convolution modulo $N$, where $N$ is 4 here. For finite length sequences product of DFT of 2 sequences is equivalent to DFT of circular-convolution of the 2 sequences.

&gt;&gt; cconv([0,1,2,1], [0,1,-1,1], 4)

ans =

 0     1     2     1




&gt;&gt;ifft(fft([0,1,2,1]).*fft([0,1,-1,1]))

ans =

 0     1     2     1