NNCP is an experiment to build a practical lossless data compressor with neural networks. The latest version uses a Transformer model. The papers nncp_v2.1.pdf and nncp.pdf describe the algorithms and results of previous releases of NNCP. The current release of NNCP is implemented in C and uses LibNC to get better performance than PyTorch. Compression ratio Result for enwik8: Program Compr. size (