Regina is a software package for 3-manifold and 4-manifold topologists, with a focus on triangulations, normal surfaces and angle structures.
For 3-manifolds, it includes high-level tasks such as 3-sphere recognition, connected sum decomposition and Hakenness testing, comes with a rich database of census manifolds, and incorporates the SnapPea kernel for working with hyperbolic manifolds. For 4-manifolds, it offers a range of combinatorial and algebraic tools, plus support for normal hypersurfaces.
Regina comes with a full graphical user interface, as well as Python bindings and a low-level C++ programming interface.
This package includes the graphical user interface and the command-line Python interface. The users' handbook and the API documentation are in the separate package regina-normal-doc, and the MPI-enabled utilities for high-performance clusters are in the separate package regina-normal-mpi.