Frequently asked questions

A list of FAQs which didn't find their way into this list can be found in the Bug Tracking System.

Installation

How do I start my own project?

First you have to get DUNE itself. This is explained in the installation notes. Then use the Dune project generator to create a simple application framework. This is done by going to where you want your application to be, and typing

   dune-common/bin/duneproject

The program will ask you for a project name, an initial version number and a maintainer's email. Supply all this and you get a new directory named after your project. In the directory you will find a sample .cc-file, the necessary AutoTools infrastructure and a README which tells you how to proceed from there.

configure fails if no f77 compiler is found.

If there is no fortran compiler installed, configure should work. If this is not the case, please reopen bug #185.

Problems occur, if there is a fortran compiler installed but it does not match the C-compiler you are using (e.g. icc together with g77), because the tests try to link fortran from C, which cannot work.

A workaround (and crude hack) is to set F77=true. In this case the test sees that it cannot compile any fortran code and just warns about it.

What Software do I need to use DUNE?

In order to build Dune you need at least the following software:

• a standard compliant C++ compiler [ tested are g++ (>= 3.4.1) and icc (7.0, 8.0 and 9.0)]
• pkg-config

When building the development version of Dune you will also need

• automake (>= 1.5)
• autoconf (>= 2.50)
• libtool

This will provide you with the core Dune features. The different grid managers like Albert or UG have to be downloaded separately.

How do I set my favourite compiler options with this fancy build-system?

You can find information about this in the build system documentation

The Grid interface

Does a Grid Implementation Have to Provide Entities of all Codimensions?

The DUNE grid interface contains methods for access to grid entities of all codimensions. However, for some entities such as faces and edges in a 3d grid, this is sometimes difficult to implement. Also, most PDE codes will not need them anyways. Therefore, currently grid implementations are only required to provide vertices and elements. All others are optional. Please refer to the documentation for the individual grids to see what codimensions they implement.

Lagrangian finite elements of order higher than one have degrees of freedom on edges and faces. In order to implement them you don't need the actual entities, just getting their indices is enough. Therefore, the method subIndex<codim>() of IndexSet is required to be implemented for all codimensions.

Is There a Way to Organize a Grid in Separate Subdomains?

Some grid managers assign a domain id to each element. Using this id the grid can be viewed as consisting of several subdomains. Each subdomain can then, for example, have different material properties. Currently the DUNE grid interface does not contain this concept. There has been discussion about including it but so far nothing happened.

One reason for this omission is that the functionality is not strictly necessary. An element's domain id is element data just like a piecewise constant FE function. You can maintain a vector with the element ids in your application and feed it to your problem assembler to let it choose your material parameters correctly.

Why does UGGrid run out of memory way before my physical memory is exhausted?

When working with UGGrid you may experience crashes with a message

   ERROR in low/heaps.c/GetFreelistMemory: not enough memory for 40 bytes.
   ERROR in low/heaps.c/GetFreelistMemory: not enough memory for 40 bytes.
   uggridtest: heaps.c:647: void* UG::GetFreelistMemory(UG::HEAP*, UG::INT): Assertion `0' failed.

even though you expect your machine to have sufficient main memory. The reason for this lies in the design of the UG grid manager. UG implements its own memory management. When creating a grid, a certain quantity of memory is allocated once, and used for all subsequent grid operations. If this quantity of memory is exhausted you get the error message above.

The default memory size is set to 500MB per grid. You can set it to other values by using the UGGrid constructor

   UGGrid (unsigned int heapSize=500);