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AutoPas is an open-source C++ library delivering optimal node-level performance by providing the ideal algorithmic configuration for an arbitrary scenario in a given short-range particle simulation. It acts as a black-box container, internally implementing an extensive set of algorithms, parallelization strategies, and optimizations that are combined dynamically according to the state of the simulation via auto-tuning. This paper gives an overview of the high-level user perspective, as well as the internal view, covering the implemented techniques and features. The library is showcased by incorporating it into the codes LAMMPS and ls1 mardyn, and by investigating various applications. We further outline node-level shared-memory performance and scalability of our auto-tuning software which is comparable to LAMMPS. Program Title: AutoPas CPC Library link to program files: https://doi.org/10.17632/9kdb2p76hv.1 Developer's repository link: https://github.com/AutoPas/AutoPas Code Ocean capsule: https://codeocean.com/capsule/0391732 Licensing provisions: BSD 2-clause Programming language: C++17, CMake 3.14 Nature of problem: The evaluation of the short-range pairwise interactions in an N-Body simulation can be achieved using many different algorithms and parallelization techniques. Depending on the nature of the scenario, its current state, and the forces of interest, the optimal algorithm configuration can differ greatly. Choosing this optimum is a non-trivial task even for experts. Furthermore, this optimum can change over the course of a simulation. Typically, a particle simulation software only implements one algorithm for force computation and is thus specialized for a certain type of simulation. It is up to the user to choose the program suitable for his needs. Solution method: The AutoPas library implements a range of state of the art algorithms to find the relevant neighbors for the N-Body pairwise force calculation. It provides multiple shared-memory parallelization strategies using OpenMP and further algorithm optimization parameters that can all be set at run-time. A big burden for users persists in requiring the expert knowledge to pick the optimal solution procedure for a simulation. AutoPas removes this burden by tuning all aforementioned options automatically and dynamically. This way, simulation programs that make use of AutoPas give every domain scientist the possibility to make use of the most suitable algorithm configuration for arbitrary scenarios. [ABSTRACT FROM AUTHOR]

UnDiFi-2D , an open source (free software) Un structured-grid, Di scontinuity Fi tting code, is presented. The aim of UnDiFi-2D is to model gas-dynamic discontinuities in two-dimensional (2D) flows as if they were true discontinuities of null thickness that bound regions of the flow-field where a smooth solution to the governing PDEs exists. UnDiFi-2D therefore needs to be coupled with an unstructured CFD solver that is used to discretize the governing PDEs within the smooth regions of the flow-field. Two different, in-house developed, CFD solvers are also included in the current distribution. The main features of the UnDiFi-2D software can be summarized as follows: Programming language UnDiFi-2D is written in standard Fortran 77/95; its design is highly modular in order to enhance simplicity of use, maintenance and allow coupling with virtually any existing CFD solver; Usability, maintenance and enhancement In order to improve the usability, maintenance and enhancement of the code also the documentation has been carefully taken into account. The git distributed versioning system has been adopted to facilitate collaborative maintenance and code development; Copyrights UnDiFi-2D is a free software that anyone can use, copy, distribute, change and improve under the GNU Public License version 3. The present paper is a manifesto of the first public release of the UnDiFi-2D code. It describes the currently implemented features, which are the result of more than a decade of still ongoing CFD developments. This work is focused on the computational techniques adopted and a detailed description of the main characteristics is reported. UnDiFi-2D capabilities are demonstrated by means of examples test cases. The design of the code allows to easily include existing CFD codes and is aimed at ease code reuse and readability. Program title: UnDiFi-2D CPC Library link to program files: https://doi.org/10.17632/5hwssmc2mx.1 Licensing provisions: GNU General Public License, version 3 Programming language: Fortran; developed and tested with Intel Fortran Compiler v. 18.0.3 and GNU gfortran. External routines: The code depends on several libraries and third-party packages which are detailed in the corpus of the text. Nature of problem: Numerical computation of flows with discontinuities. Solution method: Shock-fitting technique. Additional comments including restrictions and unusual features: • At present, UnDiFi-2D is validated for inviscid steady and unsteady two-dimensional flows without changes in the number of discontinuity lines and interaction points. • UnDiFi-2D implements a shock-fitting algorithm and can be coupled with unstructured cell-vertex solvers, with an Arbitrary Lagrangian-Eulerian (ALE) formulation. • UnDiFi-2D project adopts git [1], a free and open source distributed version control system. A public repository dedicated to UnDiFi-2D project [2] has been created on github [3], a web-based hosting service for software development projects using git versioning system. Finally, a comprehensive documentation is provided in the form of user manual developed in Pandoc [4]. [1] Git, a free and open source distributed version control system, http://git-scm.com. [2] UnDiFi-2D documentation, https://github.com/UnDiFi/UnDiFi-2D. [3] Github, a web-based hosting service for software development projects using git versioning system, https://github.com. [4] M. Dominici, TUGboat 35(1) (2014) 44-50. [ABSTRACT FROM AUTHOR]