What is Chainer?
Chainer is an open-source deep learning framework for Python, developed by the Japanese company Preferred Networks. It popularised the 'define-by-run' approach, in which the neural network is built while the computation runs, making it easier to experiment with flexible model structures. Since December 2019 Chainer has only been maintained, not further developed; Preferred Networks moved to PyTorch, which follows the same principle.