Carpet Version 3

The release branch for Carpet Version 3 was created on September 26, 2006. Version 3 has several major improvements over version 2; all users of version 2 should consider updating.

Special thanks appertain to Luca Baiotti, Ian Hawke, Christian D. Ott, Thomas Radke, Jonathan Thornburg, and Steve White for their contributions.

Here is a list of the major changes:

Grid hierarchy

• Carpet has improved support for dynamic regridding. Thorn CarpetRegrid can automatically coalesce overlapping regions, which simplfies specifying refined regions. A new Cactus schedule bin preregrid was introduced where thorns can schedule routines that decide on a new grid structure.
• It is not necessary any more to allocate all storage for all variables at all times, i.e., it is now reasonably possible to honour the STORAGE statements in the schedule. This is done by the parameter setting Carpet::enable_all_storage = no, and it can unsurprisingly reduce the memory requirements considerably. This is not yet the default setting.
• Carpet checks whether the grid hierarchy is properly nested. This is only an advice, not a requirement, since a not properly nested grid hierarchy is technically still well defined. It is sometimes surprising how many grid points per level are required for proper nesting.
• Checkpointing stores the grid hierarchy, so that it can be automatically faithfully recovered. This requires the parameter settings Carpet::regrid_during_recovery = no and CarpetIOHDF5::use_grid_structure_from_checkpoint = yes. This is not yet the default setting.

Performance

• Carpet scales better on multiple processors.
• Several of Carpet's internal administrative calculations are faster
• Carpet has timing and memory statistics, which help users determine on what parts of a simulation the time is spent

I/O

• A new thorn CarpetIOBasic replaces the old IOBasic, providing more convenient screen output. It performs global reductions over the whole grid hierarchy instead of one reduction per refinement level.
• CarpetIOASCII produces one-dimensional output along the diagonal.
• Each output file is annotated with a unique build id and a unique simulation id, so that files can be associated with the run and source tree that produced them. This requires thorn Formaline to be active.

Interpolation

• CarpetLib provides WENO (Weighted Essentially Non-Oscillatory) prolongation operators for hydrodynamics simulations. CarpetLib had already support for TVD and ENO operators, in addition to the standard Lagrange operators.
• CarpetInterp supports using non-standard (but still uniform) coordinate systems, allowing interpolating in grid arrays. Several serious errors in CarpetInterp were corrected.

Multi-patch and multi-model

• Checkpointing and recovery with multiple grid patches was corrected.
• Different grid patches can have different (local) grid spacings and different numbers of grid points.
• There is initial support for multi-model simulations. These are essentially independent simulations which are coupled only e.g. through a boundary condition between two disjoint domains containing different physical systems.

Documentation and utilities

• Carpet's documentation was improved. In particular, the schedule skeleton is now documented, describing which schedule bins and which other actions occur in what order.
• A variety of utilities for post-processing Carpet output were added or improved, e.g. for convertion Carpet ASCII output to the ygraph format, or for extracting certain pieces of HDF5 files.

Smallish things

• Many small errors were corrected
• Many small features were added
• Some error messages were improved
• Many superfluous warning messages were removed
• Carpet is now used by eleven relativity groups in the world.
• I'm looking for someone to make these web pages look nicer.

Go back to the Carpet home page.