Finally, most modern neural networks are built using computation graph formalisms that make it easy and natural to do gradient computation and parallelization onto vector-based GPUs (Graphic Processing Units). PyTorch (Paszke et al., 2017) and TensorFlow (Abadi et al., 2015) are two of the most popular. The interested reader should consult a neural network textbook for further details; some suggestions are at the end of the chapter.