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This repository contains the core functionality of UG4. Includes sources, build-scripts and utility-scripts

Copyright 2009-2023 Goethe Center for Scientific Computing, Goethe-University Frankfurt am Main

Please install/clone this repository through UG4's package manager ughub.

Introduction to UG4

UG4 is an extensive, flexible, cross-platform open source simulation framework for the numerical solution of systems of partial differential equations. Using Finite Element and Finite Volume methods on hybrid, adaptive, unstructured multigrid hierarchies, UG4 allows for the simulation of complex real world models (physical, biological etc.) on massively parallel computer architectures.

UG4 is implemented in the C++ programming language and provides grid management, discretization and (linear as well as non-linear) solver utilities. It is extensible and customizable via its plugin mechanism. The highly scalable MPI based parallelization of UG4 has been shown to scale to hundred thousands of cores.

Simulation workflows are defined either using the Lua scripting language or the graphical VRL interface https://vrl-studio.mihosoft.eu/. Besides that, UG4 can be used as a library for third-party code.

Several examples are provided in the Examples application that can be used for simulations of the corresponding phenomena but also serve as demonstration modules for implementing user-defined plugins and scripts. By developing custom plugins, users can extend the functionality of the framework for their particular purposes. The framework provides coupling facilities for the models implemented in different plugins.

The source code is commented using the Doxygen markup language.

UG4 is licensed under the LGPL v3 license with amendments. Please have a look at the accompanying LICENSE file.

Preparation of Data and Visualization of Results

The .ugx grids provided in the Examples applications can be created, visualized, and edited with ProMesh, a versatile graphical meshing solution for the generation, visualization, and preparation of computational domains for scientific computing on structured and unstructured grids. It allows users to process complicated geometries with curved boundaries and low-dimensional manifolds. ProMesh is based on UG4's grid manager and is available at http://www.promesh3d.com

promesh

The computational domain, the underlying grid, the boundary and initial conditions, as well as the problem coefficients can be specified as part of the simulation workflow in Lua scripts or the VRL-Studio GUI. However, for performance reasons, if the evaluation of the spatial and time dependence of the certain parameters is numerically expensive, one can implement those in C++, too, e.g. in a custom plugin.

Intermediate and final results of a simulation can be written to VTK's .vtu file format. These can be visualized using a number of free and open-source toolkits, e.g. ParaView http://www.paraview.org and VisIt https://wci.llnl.gov/simulation/computer-codes/visit/.

Setup and Compilation:

For the following guide, we assume the compilation is performed on a Linux/Unix machine using a standard Bash terminal. Please note that Microsoft Windows features such an environment through the free 'Ubuntu' app in the Microsoft Windows Store. If a native Windows executable is required, Visual Studio compilers can also be used.

Requirements:

For a detailed list on required software and corresponding installation instructions, please visit https://github.com/UG4/ughub

Please start by creating a UG4 root directory, e.g. $HOME/ug4. In your ug4 directory please run the following commands to obtain all required sources:

ughub init
ughub install Examples

This will clone ugcore, the Examples app and all required plugins.

Starting from UG4's root directory, please execute the following to build UG4:

mkdir build
cd build
cmake -DENABLE_ALL_PLUGINS=ON -DDIM="2;3" -DCPU="1;2" -DCMAKE_BUILD_TYPE=Release ..
make -j
cd ..

Running Examples:

Starting from UG4's root directory, please execute the following:

source ugcore/scripts/shell/ugbash
mkdir runs
cd runs
ugshell -ex Examples/poisson.lua
ugshell -ex Examples/poisson.lua -dim 3
ugshell -ex Examples/solmech.lua
ugshell -ex Examples/elder_adapt.lua
ugshell -ex Examples/navier_stokes.lua
ugshell -ex Examples/electromagnetism_pan.lua -numRefs 3

Examples:

Please make sure that you installed UG4's Examples application as described above.

Poisson Problem

A script computing the solution of the Poisson problem is given in apps/Examples/poisson.lua. The right hand side of the differential equation can be specified through a callback method in the Lua script. A projector is used during grid refinement to approximate a circle with additional refinements.

poisson

Linear Elasticity

A 3d simulation of deformation using linear elasticity is provided in apps/Examples/solmech.lua.

springboard

Density Driven Flow

An adaptive simulation of the Elder problem is provided in apps/Examples/elder_adapt.lua. A gradient based error indicator is used to refine areas of interest.

elder adaptive

Navier Stokes

Simulations of fluid flow in a channel with a cylindrical cutout are performed in apps/Examples/navier_stokes.lua.

navier_stokes

Electromagnetism (induction heating)

Simulation of the eddy currents and the corresponding heat sources induced by alternating electromagnetic field in a conductive plate is represented in apps/Examlpes/electromagnetism_pan.lua. The stationary E-based formulation of the eddy current model for the complex-valued fields is used. The discretization of the Maxwell equations is done by the Nedelec elements on a tetrahedral grid. This example demonstrates in particular the projection of the refined elements to the curved boundaries in 3d.

heat

UG4 for VRL-Studio:

VRL-Studio is an innovative and powerful IDE for rapid prototyping, learning, teaching and experimentation. It introduces Visual Reflection for automatic user interface generation. It combines textual and visual programming in an intuitive user interface. UG4 provides a built-in VRL binding that allows to setup and execute visual simulation workflows from VRL-Studio. The supplementary VRL-Studio folder contains a precompiled version of VRL-Studio which includes UG4 and a sample project to briefly demonstrate UG4s capabilities as VRL-Studio plugin.

Download Links for supplementary software folder:

Opening the Sample Project:

The supplementary software folder contains a version of VRL-Studio that includes a precompiled version of UG4 and additional plugins for visualization.

Running VRL-Studio on Linux:

To run VRL-Studio from the supplementary software folder, execute the following commands:

cd path/to/VRL-Studio-For-UG4
./run.sh

Running VRL-Studio on macOS:

For macOS, VRL-Studio is provided as application bundle. Simply double-click the application bundle to run VRL-Studio.

Running VRL-Studio on Windows:

For Windows, VRL-Studio is provided as application bundle. Just run the VRL-Studio.exe file inside the VRL-Studio folder.

If VRL-Studio runs for the first time, it will install several plugins (e.g. the UG4 plugin) before showing the main user interface.

To open the sample project, click on File->Load Project and navigate to the sample project (skin-2d.vrlp).

Now do the following:

  1. Select the desired output file (for this example vtk-output/skin-2d.vtu).
  2. Select the desired geometry (for this example skin-2d.ugx).
  3. Press Start to run the simulation.
  4. Check the log window for simulation progress (click on View->Show Log in Window or drag up the divider at the bottom of the VRL-Studio main window to reveal the log).
  5. The vtk-output/ folder contains the simulation output that can be post-processed with a VTK viewer such as ParaView.

vrl-skin2d

Compiling UG4 for VRL-Studio:

The following steps explain how to manually compile UG4 for VRL-Studio.

In addition to the aforementioned requirements, compilation for VRL-Studio requires Java (JDK >= 1.8). Additionally, VRL-Studio needs to run at least once to make sure the required folder structure is created.

To build UG4 as shared library for VRL-Studio, different CMake options have to be used. The following commands build UG4 for VRL-Studio:

cd path/to/ug4
mkdir build_vrl && cd build_vrl
cmake .. -DTARGET=vrl -DLAPACK=OFF -DBLAS=OFF -DDIM=ALL -DCPU="1;2" -DCOMPILE_INFO=OFF -DEMBEDDED_PLUGINS=ON -DSTATIC_BUILD=OFF
make -j

After successful compilation, the shared library libug4.so (libug4.dylib on macOS and ug4.dll on Windows) needs to be copied to the VRL plugin folder. For VRL-Studio installed from the supplementary software folder, the following command can be used to copy the shared library to the correct plugin folder:

cp path/to/libug4.so $HOME/.vrl/0.4.3/default-ug4/plugins/VRL-UG/natives/linux/x64/

After restarting VRL-Studio, the new library is used.

Further Documentation:

Installation instructions are given at https://github.com/UG4/ughub

Further documentation on UG4 is available at http://ug4.github.io/docs/

Please have a look at http://ug4.github.io/docs/page_external_libraries.html for more information on used libraries and their licenses.

Related Articles:

  Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G.
  A massively parallel geometric multigrid solver on hierarchically distributed grids.
  Computing and visualization in science 16, 4 (2013), 151-164,
  DOI: 10.1007/s00791-014-0231-x

  Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G.
  UG4 -- a novel flexible software system for simulating pde based models on high performance computers.
  Computing and visualization in science 16, 4 (2013), 165-179,
  DOI: 10.1007/s00791-014-0232-9

(Cf. the bib-file in the ugcore directory.)