in the backward propagation process:

acquiring a bit-vector including bits indicating which of output activations of forward propagation operation of a layer of the neural network are zero or non-zero, the bit-vector having been generated in a process of a forward propagation of the neural network, with input activations of the layer in the backward propagation process respectively corresponding to the output activations;

selecting, based on bits of the bit-vector indicating which of the input activations have values of 0, only non-zero activations and corresponding filters respectively from among the input activations and forward propagation filters of the layer used in the forward propagation operation;

generating backward propagation filters of the layer by rearranging the selected corresponding filters, where there are fewer generated backward propagation filters than forward propagation filters;

generating zero padded activations by performing zero padding on the selected non-zero activations; and

performing the backward propagation using the zero padded activations and the backward propagation filters,

wherein the selecting of the non-zero activations comprises selecting the non-zero activations based on an interpreting of the bits included in the bit-vector for a total number of the selected non-zero activations based on a total number of multipliers available for the performance of the backward propagation, or until the total number of the selected non-zero activations equals the total number of multipliers.