# About

The `xerus`

library is a general purpose library for numerical calculations with higher order tensors, Tensor-Train Decompositions / Matrix Product States and other Tensor Networks. The focus of development was the simple usability and adaptibility to any setting that requires higher order tensors or decompositions thereof.

For tutorials and a documentation see the documentation.

The source code is licenced under the AGPL v3.0. For more details see the LICENSE file.

# Features

- Intuitive notation for expressions involving tensors of arbitrary degree:
`A(i,j) = B(i,k,l) * C(k,j,l)`

; - Lazy evaluation of tensor expressions with automatically optimized contraction orders.
- Full implementation of all common functionality of the Tensor Train (or Matrix Product State) decompositions with either dense or sparse component tensors.
- Implementations of common algorithms like the ALS, (multi-site-)DMRG, ASD, AFD, CG, and some less common ones e.g. to find the maximal entries in a Tensor Train.

# Building the Xerus library

Copy the default configuration and modify it for your needs

cp config.mk.default config.mk

nano config.mk

Test whether everything works correctly with

make test -j4

build (and optionally install) the library with

make all -j4

sudo make install

and you should be ready to use the library. For more details see the "Building Xerus" page in the documentation.

# Issues

Should you have any problems with the library do not hesitate to contact us at contact[at]libxerus.org or describe your problem in the issuetracker.