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Overview

Autogen is an automatic expression generator for second-quantized many-body expressions using Wick’s theorem and a home for reviewed method implementations generated from that algebra.

It is designed to generate algebraic expressions in the same “diagram-style” symbolic form commonly used in electronic structure theory derivations (e.g., coupled cluster and unitary coupled cluster).

What it produces

  • Lists of symbolic “terms” representing operator strings, contractions, delta factors, and prefactors.
  • LaTeX-friendly output via the printing utilities.

Key features

  • String-based operator specification (e.g., ['V2'], ['T1']) with internal expansion to operator objects.
  • Recursive handling of nested commutators (innermost-first).
  • Support for de-excitation operators (e.g., D1, D2) to enable UCC-style algebra.

In particular, features like de-excitation support and nested commutators (e.g. [[V2, T1], D1]) make Autogen suitable for unitary coupled cluster (UCC) style derivations.

Package layout

  • autogen.library – core term/operator structures and utilities
  • autogen.main_tools – commutator/product/driver orchestration
  • autogen.pkg – EWT/GWT utilities
  • autogen.methods.ccsd – CCSD derivation, generated kernels, and runtime
  • autogen.methods.eom_ccsd – EOM-CCSD derivation, generated kernels, and runtime
  • autogen.methods.qpccsd – projected-AGP QPCCSD and fixed-amplitude PAV

Method implementations are installable package modules. Checkout-only generated-code paths and campaign copies are not public APIs.

Next: see usage.md for runnable examples.