TNSPackage: A Fortran2003 library designed for tensor network state methods

Recently, the tensor network states (TNS) methods have proven to be very powerful tools to investigate the strongly correlated many-particle physics in one and two dimensions. The implementation of TNS methods depends heavily on the operations of tensors, including contraction, permutation, reshaping tensors, SVD and so on. Unfortunately, the most popular computer languages for scientific computation, such as Fortran and C/C++ do not have a standard library for such operations, and therefore make the coding of TNS very tedious. We develop a Fortran2003 package that includes all kinds of basic tensor operations designed for TNS. It is user-friendly and flexible for different forms of TNS, and therefore greatly simplifies the coding work for the TNS methods.

近年来，张量网络态（Tensor Network States，TNS）方法已被证明是研究一维和二维强关联多粒子物理的极为强大的工具。TNS方法的实现高度依赖各类张量运算，包括张量收缩、置换、张量重塑、奇异值分解（Singular Value Decomposition，SVD）等。遗憾的是，当前主流的科学计算编程语言，如Fortran和C/C++，并未针对这类运算提供标准库，这使得TNS方法的编码工作极为繁琐。为此，我们开发了一款专为TNS设计的Fortran2003软件包，涵盖所有基础张量运算。该软件包易用性强、灵活性佳，可适配多种形式的TNS方法，极大简化了TNS方法的编码工作。