Migration guide

This page collects notes for upgrading between MPSKit releases when a change requires action on your side. It summarizes the breaking changes recorded in the Changelog; consult that page for the complete, per-version list of changes.

Unreleased

environments now uses a single positional contract

environments now follows one positional contract for every state and operator kind:

environments(below, operator, above, alg)

where alg (slot 4) is the environment algorithm. The operator form requires an explicit above argument. Auxiliary inputs are now keyword-only: leftstart/rightstart for finite and window environments, and lenvs/renvs for window and quasiparticle environments.

The two-argument form environments(below, above) (two states) is reserved for the operator-free overlap environments. There is no two-argument environments(below, operator) shorthand: a two-argument call is always interpreted as an overlap, because the second argument cannot be disambiguated between a ket and an operator (this is undecidable for density matrices, where states and operators share a representation). If you previously relied on a two-argument operator call, pass the operator explicitly with an above state. See #436.

Earlier releases

The Changelog records further changes across the 0.13.x series, including a refactor of the IDMRG implementation to the IterativeSolver interface (#348), fixes to changebonds consistency (#415), and a refactor of time-evolution MPO construction (#422).