PyTorch

PyTorch is the open-source deep learning framework that dominates academic and industrial research, largely because its define-by-run execution lets models be written and debugged like ordinary Python. Tensors behave like NumPy arrays with GPU acceleration, and autograd records operations to compute gradients automatically, so experimental architectures iterate quickly.

Production readiness is no longer the gap it once was: torch.compile compiles models for speed, FSDP and related tooling distribute training across clusters, and TorchServe or ONNX export handle deployment. The surrounding ecosystem is a large part of its pull, from torchvision and torchaudio to Hugging Face Transformers, and most new papers ship PyTorch code first. Governed by the PyTorch Foundation under Linux, it suits researchers, ML engineers, and teams training custom models; it rewards Python fluency and is heavier than Keras-style APIs for newcomers.