[ET Trac] [Einstein Toolkit] #2064: Add GiRaFFE to the Einstein Toolkit

Einstein Toolkit trac-noreply at einsteintoolkit.org
Fri Aug 4 12:02:04 CDT 2017

#2064: Add GiRaFFE to the Einstein Toolkit
 Reporter:  zachetie@…                     |       Owner:                     
     Type:  enhancement                    |      Status:  new                
 Priority:  unset                          |   Milestone:                     
Component:  EinsteinToolkit thorn          |     Version:  development version
 Keywords:  GiRaFFE, GRFFE, IllinoisGRMHD  |  
 We (the authors of GiRaFFE) hereby request that GiRaFFE be added to the
 Einstein Toolkit. In short, GiRaFFE is the first open source, dynamical-
 spacetime code for modeling plasma flows in general relativistic force-
 free electrodynamics (GRFFE). It will be the best code in the Toolkit for
 modeling black hole and neutron star magnetospheres, as these
 magnetically-dominated regions are best modeled numerically by a GRFFE
 code (GRMHD codes break down when modeling very highly magnetized

 Here is the commit ID for code reviewer comments:

 Here is the original release announcement to the mailing list, including
 link to the code release paper:

 We are pleased to announce the public release of GiRaFFE, an open-source
 General Relativistic Force-Free Electrodynamics (GRFFE) code for dynamical

 -= Code Release Paper =-
 Our code release paper--including a full description of the GiRaFFE code,
 a discussion of potential applications of GiRaFFE, and code validation
 test results--has been uploaded to the arXiv:
 https://arxiv.org/abs/1704.00599 .

 -= Executive Summary =-
 GiRaFFE adopts the strategy pioneered by McKinney [1] and modified by
 Paschalidis and Shapiro [2] to convert a general relativistic
 magnetohydrodynamic (GRMHD) code into a GRFFE code. In short, GiRaFFE
 exists as an extensive modification to IllinoisGRMHD [3]. Both GiRaFFE and
 IllinoisGRMHD leverage the Einstein Toolkit’s highly-scalable
 infrastructure [4,5] to make possible large-scale simulations of
 magnetized plasmas in strong, dynamical spacetimes on adaptive-mesh
 refinement (AMR) grids.

 As you are aware, IllinoisGRMHD is an open-source rewrite of the Illinois
 Numerical Relativity Group's GRMHD code. GiRaFFE, on the other hand, is
 not based on any existing GRFFE code and is designed only to solve the
 equations of GRFFE in the context of fixed or dynamically-generated
 spacetimes. GiRaFFE has passed a large suite of GRFFE code validation
 tests passed by other state-of-the-art GRFFE codes, leading us to conclude
 that GiRaFFE is now ready for large-scale, state-of-the-art GRFFE
 simulations in dynamical spacetimes.

 -= New Thorns for the Einstein Toolkit =-
 All GiRaFFE thorns are listed below. Next to the name of each thorn, we
 include the number of lines of code to highlight the fact that GiRaFFE is
 quite compact and designed to be welcoming to new users. In addition, the
 comment-to-line-of-code ratio is very nearly 50%, and the code release
 paper provides a clean, broad-brush overview of the formalism and
 algorithms adopted. To become acquainted with any given thorn, first take
 a look at its README file.

 * GiRaFFE (~1,600 lines of code): Solves the GRFFE equations in the
 formalism of Paschalidis & Shapiro [2] using the same reconstruction (PPM)
 and staggered vector potential methods as IllinoisGRMHD.

 * GiRaFFEfood (~1,300 lines of code): Code validation initial data and
 basic diagnostics. Contains
 Five 1D tests in flat spacetime (fast wave, Alfvén wave, degenerate Alfvén
 wave, "three-wave", FFE breakdown),
 One 3D test in flat spacetime (aligned rotator), and
 Three 3D tests in curved spacetimes ("Exact Wald" solution,
 "Magnetospheric Wald" solution, and split monopole).
 * ShiftedKerrSchild (~230 lines of code): Sets up all 3+1 quantities for a
 Kerr-Schild spacetime with an arbitrary radial shift, to mitigate effects
 of extreme spacetime curvature near r_{KS}=0. See Appendix of code release
 paper for full discussion.

 * VolumeIntegrals_slab_Gfood (~310 lines of code): Performs volume
 integrals over arbitrary rectangular prisms as specified in parameter

 * GiRaFFE_to_HydroBase & ID_converter_GiRaFFE (~230 lines of code): Acts
 as a translation layer to convert 3-velocities in HydroBase's Valencia
 formalism to/from the 3-velocity found in the induction equation (v^i =
 u^i/u^0; native to GiRaFFE).

 -= License =-
 To maximize compatibility with existing thorns in ET, all of the
 aforementioned GiRaFFE thorns are either licensed GPLv2+ or 2-clause BSD
 (FreeBSD). See LICENSE file in each.

 -= Download GiRaFFE! =-
 The collection of thorns comprising GiRaFFE may be downloaded here:


 The GiRaFFE team

 -Zach Etienne
 -Mew-Bing Wan
 -Maria Babiuc
 -Sean McWilliams
 -Ashok Choudhary

 [1] J.C. McKinney. Mon. Not. R. Astron. Soc., 367:1797, 2006.
 [2] V. Paschalidis and S. L. Shapiro. Phys. Rev. D, 88:104031, 2013.
 [3] Z. B. Etienne, V. Paschalidis, R. Haas, P. M¨osta, and S. L. Shapiro.
 Class. Quantum Grav., 32(17):175009, 2015.
 [4] https://einsteintoolkit.org/
 [5] https://carpetcode.org/

Ticket URL: <https://trac.einsteintoolkit.org/ticket/2064>
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