  We describe a general-purpose computational toolkit for simulating open
quantum systems, which provides numerically exact solutions for composites of
zero-dimensional quantum systems that may be strongly coupled to multiple,
quite general non-Markovian environments. It is based on process tensor matrix
product operators (PT-MPOs), which efficiently encapsulate environment
influences. The code features implementations of several PT-MPO algorithms, in
particular, Automated Compression of Environments (ACE) for general
environments comprised of independent modes as well as schemes for generalized
spin boson models. The latter includes a divide-and-conquer scheme for periodic
PT-MPOs, which enable million time step simulations for realistic models.
PT-MPOs can be precalculated and reused for efficiently probing different
time-dependent system Hamiltonians. They can also be stacked together and
combined to provide numerically complete solutions of small networks of open
quantum systems. The code is written in C++ and is fully controllable by
configuration files, for which we have developed a versatile and compact
human-readable format.
