We are pleased to announce the thirty-first release (code name "Hypatia") of the Einstein Toolkit, an open-source, community-developed software infrastructure for relativistic astrophysics. The major changes in this release include:
New thorns in this release:
Cottonmouth (CottonmouthBSSNOK4m, CottonmouthZ4c4m, CottonmouthGaugeWaveID, CottonmouthLinearWaveID) -- A new suite of GPU-accelerated spacetime evolution thorns for CarpetX, generated using the Einstein Engine code generator. CottonmouthBSSNOK4m and CottonmouthZ4c4m implement the BSSNOK and Z4c formulations of Einstein's equations with 4th-order stencils and matter support; CottonmouthGaugeWaveID and CottonmouthLinearWaveID provide corresponding test initial data.
CanudaX (CanudaX_BSSNMoL, CanudaX_NPScalars, CanudaX_ExactID) -- A new GPU-accelerated BSSN spacetime evolution suite for CarpetX, based on the Canuda library. Includes a BSSN evolution thorn, Newman-Penrose scalar Psi4 extraction, and exact initial data (Kerr, Teukolsky waves, Apples-with-Apples test cases).
KerrSchildX -- A new thorn in SpacetimeX providing Kerr-Schild initial data for single spinning black holes, for use with the CarpetX driver.
TwoPuncturesX -- A new thorn providing a C++ interface to TwoPunctures binary black hole initial data, for use with the CarpetX driver.
Updated thorns and components:
CarpetX -- Added support for integer and complex grid array and scalar types; custom OpenMP reductions for NVIDIA HPC SDK compiler compatibility; named OpenMP critical sections; pinned Particles in interpolation.
ET_BHaHAHA -- Added SphericalSurface export support; updated to latest BHaHAHA version with additional bug fixes and a reproducible regeneration Makefile.
GRHayL -- Added Noble2D con2prim for tabulated equations of state; generalized and cleaned con2prim backup strategy; new tabulated EOS reader; Doxygen documentation added.
GRHayLHD/GRHayLHDX -- Updated to use new tabulated EOS reader and new GRHayL API; fixed schedule to correctly use volume integrals group.
TOVola -- Bug fixes for Lagrange interpolation stability; regression tests made surface-aware; updated for new GRHayL API.
AHFinderDirect -- Fixed regex patterns in param.ccl for improved portability.
TwoPunctures -- Refactored to C++ with namespace isolation, enabling the new TwoPuncturesX thorn; added W-type precollapsed lapse option.
NewRadX -- Added support for CapyrX multipatch grids.
QuasiLocalMeasures -- Corrected sign in ADM linear momentum calculation.
SummationByParts -- Fixed duplicated switch construction and 4th-order second derivative operator scheduling.
CCE_Export -- Added configurable array size parameter; minor documentation and portability fixes.
POWER -- Fixed detection of smallest timestep across radii; cleaned up output formatting.
Llama -- Fixed inconsistent volume calculation.
fuka -- Substantial development: ability to restart from a previous solution; improved grid setup and shell spacing for BNS/BHNS/BBH systems; improved handling of high mass-ratio cases; backward-compatible import of old initial data formats.
LeanBSSNMoL -- Removed explicit Cray pointer variable declarations for improved portability.
SphericalSurface -- Scheduling fix to ensure Set runs after Setup.
Kuibit -- Bumped to 1.6.1.
Updated external libraries:
AMReX -- Updated to version 25.11; added configurable CUDA architecture selection.
ADIOS2 -- Added missing stdint.h include for compatibility with GCC 15; improved MPI library handling.
Boost -- New external library thorn added.
GSL -- Updated to GSL 2.8.
HDF5 -- Improved system library path detection.
PETSc -- Updated to PETSc 3.23.4.
Silo -- Build fix: disabled config-site directory reading.
In addition, bug fixes accumulated since the previous release have been included, as well as stability and optimization improvements through Simfactory.
The Einstein Toolkit is a collection of software components and tools for simulating and analyzing general relativistic astrophysical systems. It builds on numerous software efforts in the numerical relativity community, including codes to compute initial data parameters, the spacetime evolution codes Baikal, lean_public, McLachlan, CanudaX, and Cottonmouth, analysis codes to compute horizon characteristics and gravitational waves, and the relativistic (magneto)hydrodynamics codes GRHayLHD, GRHayLHDX, GRHydro, and IllinoisGRMHD. Data analysis and post-processing are handled by the kuibit library. The Einstein Toolkit also contains a 1D self-force code. The toolkit supports two AMR drivers: the established Carpet infrastructure, and the newer CarpetX infrastructure built on the AMReX framework, which adds support for GPU acceleration and block-structured adaptive mesh refinement on modern supercomputing architectures. For parts of the toolkit, the Cactus Framework is used as the underlying computational infrastructure, providing large-scale parallelization, general computational components, and a model for collaborative, portable code development.
The Einstein Toolkit uses a distributed software model. Its different modules are developed, distributed, and supported either by the core team of Einstein Toolkit Maintainers or by individual groups. Where modules are provided by external groups, the Einstein Toolkit Maintainers ensure quality control for modules included in the toolkit and help coordinate support. The Einstein Toolkit Maintainers currently involve staff and faculty from five different institutions and host weekly meetings that are open to anyone.
Guiding principles for the design and implementation of the toolkit include: open, community-driven software development; well thought-out and stable interfaces; separation of physics software from computational science infrastructure; provision of complete working production code; training and education for a new generation of researchers.
For more information about using or contributing to the Einstein Toolkit, or to join the Einstein Toolkit Consortium, please visit our web pages at http://einsteintoolkit.org, or contact the users mailing list users@einsteintoolkit.org.
The Einstein Toolkit is primarily supported by NSF 2411068 (E=mc2: Enabling Multimessenger astrophysics through Community-driven Cyberinfrastructure) and NSF 2004157/2004044/2004311/2004879/2003893/2114582/2227105 (Enabling fundamental research in the era of multi-messenger astrophysics).
The Einstein Toolkit contains about 400 regression test cases. On a large portion of the tested machines, almost all of these tests pass, using both MPI and OpenMP parallelization.
Among the many contributors to the Einstein Toolkit and to this release in particular, important contributions to new and existing components were made by the following authors:
Alexandru Dima
Benjamin Meyers
Beyhan Karakas
Bruno Giacomazzo
Cheng-Hsin Cheng
Chloe Richards
David Boyer
Deborah Ferguson
Erik Schnetter
Gabriele Bozzola
Giuseppe Ficarra
Jake R. Doherty
Leonardo Werneck
Liwei Ji
Lucas Timotheo Sanches
Marco Brito
Maxwell Rizzo
Max Morris
Noora Ghadiri
Peter Diener
Rahime Matur
Roland Haas
Samuel Cupp
Samuel Tootle
Steven R. Brandt
Zachariah B. Etienne
To upgrade from the previous release, use GetComponents with the new thornlist to check out the new version.
See the Download page (http://einsteintoolkit.org/download.html) on the Einstein Toolkit website for download instructions.
The SelfForce-1D code uses a single git repository; thus, using
git pull; git checkout ET_2026_05
will update the code.
To install Kuibit, do the following:
pip install --user -U kuibit==1.6.1
Debian, Ubuntu, Fedora, Mint, OpenSUSE, and macOS installations with dependencies installed as prescribed in the official installation instructions
Anvil
Deep Bayou
Delta
Expanse
Frontera
Queen Bee 3 and 4
Stampede 3
Sunrise
Supermike
sourcebasedir = $WORK and basedir = $SCRATCH/simulations configured for this machine. You need to determine $WORK and $SCRATCH by logging in to the machine.All repositories participating in this release carry a branch ET_2026_05 marking this release. These release branches will be updated if severe errors are found.
Steven R. Brandt (release manager)
Beyhan Karakas (assistant release manager)
Roland Haas (assistant co-chair)
Bing-Jyun Tsao
Deborah Ferguson
Cheng-Hsin Cheng
Leonardo Werneck
Lucas Timotheo Sanches
Maxwell Rizzo
Noora Ghadiri
Peter Diener
Rahime Matur
Yuvraj Sharma
TBD, 2026