index.rst

cppdlr: Imaginary time calculations using the discrete Lehmann representation

cppdlr is a C++ library implementing the discrete Lehmann representation (DLR) of imaginary time single-particle Green's functions and other imaginary time quantities, including standard operations. It can be downloaded from GitHub.

The DLR has been implemented in other programming languages (see the :ref:`related libraries<otherlibraries>` below). cppdlr offers a particularly simple high-level user interface, enabled by the use of C++ templating and the nda library for array types and BLAS/LAPACK compatibility. This facilitates its use both in small-scale applications and in existing large-scale software projects such as the TRIQS library for quantum many-body calculations, which has incorporated the DLR via cppdlr.

Getting started

• Install the library by following the instructions on the :ref:`installation page<install>`.
• If you are unfamiliar with the DLR, you can read the :ref:`background page<background>` for a brief introduction, or the references below for more detail. If you are familiar with the DLR, you should still take a brief look at the :ref:`background page<background>` for important information about the library.
• To begin using cppdlr in your application, the :ref:`examples page<examples>` provides a good starting point.
• If you need more specific information about cppdlr classes and functions, take a look at the :ref:`reference documentation page<documentation>`.

References

If you use cppdlr in your software or published research works, please mention this, and cite the following references. Citations help to encourage the development and maintainence of open-source scientific software.

• The original reference on the DLR: J. Kaye, K. Chen, O. Parcollet, "Discrete Lehmann representation of imaginary time Green's functions", Phys. Rev. B, 105, 235115 (2022). [arXiv:2107.13094]
• The companion paper to cppdlr: J. Kaye, H. U. R. Strand, N. Wentzell, "cppdlr: Imaginary time calculations using the discrete Lehmann representation", arXiv:2404.02334 (2024).

Related libraries

Libraries implementing the DLR are available in other languages:

• Python, via pydlr
• Fortran, via libdlr
• Julia, via Lehmann.jl

cppdlr is also used to implement the DLR in the Toolbox for Research on Interacting Quantum Systems (TRIQS).

.. toctree::
   :maxdepth: 2
   :caption: Contents:

   install.rst
   background.rst
   examples.rst
   documentation.rst
   issues.rst