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Carpet is a mesh refinement driver for Cactus. Cactus is a framework for solving time-dependent partial differential equations on uniform grids, and Carpet is an extension of Cactus that make mesh refinement possible. Carpet was originally written in 2001 by Erik Schnetter at the TAT (Theoretische Astrophysik Tübingen) and is currently maintained at the AEI (Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut). These pages describe Carpet and its current development.
News
December 7, 2004: Jonathan Thornburg is organising a Carpet Design Walkthrough, which will take place December 13 to 15 at the AEI and will be broadcast via the accessgrid and/or telephone.
Sepbember 18, 2004: There is now a new repository for the development version of Carpet. This repository is managed by darcs instead of CVS. Darcs has a number of advantages, such as being able to use it while offline, or keeping some changes to yourself while developing. This development version is publicly available, and we encourage you to contribute. Note that the stable version of Carpet is still distributed via CVS.
August 24, 2004: The version of Carpet in the CVS repository is now stable. That means that this version will see no substantial further development. One of its main goal is to not change, so that parameter files continue to work unchanged with identical results. We will continue to correct errors that we find in this version of Carpet; however, if this would necessitate major changes, and there is a work-around, then this might not happen in the interest of stability.
July 31, 2004: Carpet seems to have reached a point where it is stable enough to be useful for at least some projects. Consequently, people expressed the wish to have a version of Carpet which is stable and sees no disrupting development. The idea is to have two "branches" of Carpet: a stable version for production use, and a development version which might not be as stable. We plan to make the split in about three weeks. The discussion about this is held on the mailing list; your input is welcome.
April 7, 2004: Up to now, all Carpet thorns have been living in a single arrangement for Cactus. This caused problems, because stable thorns, development thorns, and outdated thorns were sitting next to each other, confusing newcomers. We have moved the Carpet arrangement to a new repository and split it into four. Access to the old Carpet arrangement has been disabled.
March 3, 2004: We have recently had trouble with I/O throuth the FlexIO library. We suspect that it might have a bug that causes HDF5 output to fail under certain, random conditions. We have written a new thorn CarpetIOHDF5 which uses the HDF5 library directly, while remaining compatible to the FlexIO file format. Please test this thorn, and report any problems or incompatibilities you find.
In January 2004, Daniel Kobras set up Bugzilla for Carpet. Bugzilla is a bug-tracking system that will, so we hope, help us remember what is missing or broken in Carpet.
Documentation
We have accumulated a few pieces of documentation:
- An introduction (ps, 300 kB) to Carpet, as well as a guide to the first steps for using it. Everybody should have read this. (This is the same as the Arrangement Guide from the Carpet sources.)
- Ulrich Sperhake wrote a tutorial outlining the first steps (ps, 160 kB) that one has to take to install Carpet and run an example application.
- An explanation of the internal workings (ps, 130 kB) of Carpet. You should read this if you want to modify Carpet.
- The individual Thorn Guides of Carpet. They are available with the source code. They give details about the thorns' APIs and user interfaces.
- Thanks to Doxygen, we now have an overview over all the routines and data structures in Carpet. Most individual Doxygen tags are still missing, but the extracted documentation is already very useful. (The online documentation might not always be up to date; in case of doubt, extract the documentation yourself.)
Interacting with the developers
Most discussions about Carpet, i.e. user questions, feature requests, and bug reports, are held on the Carpet developers' mailing list developers@lists.carpetcode.org. You can subscribe and unsubscribe from our list management web page. You will also find the mailing list archive there. We thank Daniel Kobras for managing the mailing list server.
We have started to use Bugzilla to keep track of requested features or reported bugs in Carpet. You can submit or comment on issues from our Bugzilla pages once you have created an account there. The old list of missing features have not yet been moved over to Bugzilla.
Getting the code
Carpet is distributed under the GNU General Public License (GPL). It might be released under the GNU Lesser General Public License (LGPL) in the future, to match the distribution terms of Cactus.
Carpet is a driver for Cactus. It works as a part of Cactus, and you will need to have the developers' version of Cactus installed before you can use Carpet. Please look at the Cactus web pages for an introduction to Cactus and for installation instructions.
Carpet is available via anonymous CVS. The CVSROOT is
:pserver:cvs_anon@cvs.carpetcode.org:/home/cvs/carpet,
and there are several arrangements, each living in a directory.
The arrangement Carpet contains the basic driver part
that everybody needs. The arrangement CarpetExtra
contains useful add-ons and some example code. Development of new
thorns happens in the CarpetDev arrangement, which
means that the code in there is not to be trusted. And finally,
there is a graveyard arrangement CarpetAttic of
things that only used to be useful and are now in a state of
decay.
The password for anonymous CVS access is anon. We
thank the Institut für
Astronomie und Astrophysik of the Universität Tübingen for
hosting the CVS server.
Pretty pictures
Here are some pretty pictures of simulations that were performed with Carpet:
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Cut through a binary black hole system. Height field of the lapse function (approximately the time dilatation) in a binary black hole system calculated from Meudon initial data. The system is cut between the two black holes, so that only one black hole is visible. The white boxes indicate the hierarchy of refinement regions. |
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A quadrupole wave. Two rotating scalar charges create a quadrupolar wave, mimicing the gravitational wave trail of a binary black hole system. The small bumps and riddles are artifacts caused by the discontinuous charge distribution. To be improved. |
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Lapse isosurfaces in a binary black hole system. The same system as above, but the lapse function is rendered as isosurfaces. |
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A velocity component in a stellar core collapse. The x component of the fluid velocity in a stellar core collapse. This simulation was performed by Christian Ott. |
Sorry; no movies so far.
Making sense of results
Three-dimensional time-dependent simulation results are difficult enough to interpret when the grid is uniform. With mesh refinement, the sheer amount of available data makes it necessary to use professional tools to examine the data. This is not only the case for "big physics runs", where one (should) know in advance what to expect, but especially during development, where things do not always go as planned. Thomas Radke was kind enough to write an import module for the visualisation tool OpenDX.
Related projects
Last modified: Sat Jan 1 17:13:40 CET 2005