A system and method for pruning. A neural network includes a plurality of long short-term memory cells, each of which includes an input having a weight matrix Wc, an input gate having a weight matrix Wi, a forget gate having a weight matrix Wf, and an output gate having a weight matrix Wo. In some embodiments, after initial training, one or more of the weight matrices Wi, Wf, and Wo are pruned, and the weight matrix Wc is left unchanged. The neural network is then retrained, the pruned weights being constrained to remain zero during retraining.