Adding Llama to the ET

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In order to add Llama to the ET, we require:

  • Tests
  • Documentation
  • Example(s)

The Llama infrastructure has been used in many published papers, so is clearly considered robust enough to produce correct scientific results.


We have the following test cases:

  • Llama/Coordinates/test/test7patch: Sets up the 7-patch system. Checks coordinates. Makes sure that this doesn't crash. No evolution.
  • Llama/LlamaWaveToy/test/llamawavetoy_6patch.par: Sets up 6-patch (spherical) system. Evolves l=2,m=2 x Gaussian for 4 iterations. Checks 1D ASCII output. Runs on any number of processes (only 1 and 2 have been tested).
  • Llama/LlamaWaveToy/test/llamawavetoy_7patch.par: Same as 6-patch but uses 7-patch system. Works on 1 process. Currently has a problem on 2 processes; looks like a bug. Assertion failure from Carpet. Restricted to run on 1 process as a result. Ticket 1989
  • McLachlan/ML_BSSN_Test/test/ML_BSSN_MP_O8_bh.par: Runs a few iterations of BBH initial data using 8th order McLachlan on 7-patch (spherical+Cartesian) system.


There is documentation for the arrangement as a whole in the top level doc directory. This provides an introduction to the Llama multipatch infrastructure, the different patch systems and the various parameters that need to be set.

The following thorns also have their own individual documentation:

  • GlobalDerivative: Describes the multipatch-aware finite differencing implementation
  • Interpolate2: Interpatch interpolation
  • LlamaWaveToy: A scalar wave equation on various backgrounds.
  • WaveExtractL: Llama-optimised wave extraction using Zerilli-Moncrief and Regge-Wheeler gauge invariant perturbations of Schwarzschild
  • WaveExtractCPM: Llama-optimised wave extraction using Cunningham-Price-Moncrief gauge invariant perturbations of Schwarzschild

The documentation is probably not all up-to-date; some issues include:

  • The WaveExtractL documentation is copied straight from the Exact thorn and may not include changes relevant to Llama.


There are three examples in LlamaWaveToy/par:

  • Kerr-Schild_Gaussian.par: Radial Gaussian evolved with wave equation on Kerr-Schild background. Uses 6-patch (spherical) system.
  • Kerr-Schild_Multipole.par: l=2, m=2 mode with radial Gaussian evolved on a Kerr-Schild background. Uses 6-patch (spherical) system.
  • Minkowski_Multipole.par: l=2, m=2 mode with radial Gaussian evolved on a flat background. Uses 7-patch (spherical+Cartesian) system.

These run in about 20 minutes on a laptop, and evolve a wave on a given background. These have been tested and work.

There is a new Multipatch Wave Equation gallery page based on the Kerr-Schild_Multipole example (not yet linked to the main gallery page).

There is also the GW150914 gallery page.