TRUST is a High Performance Computing (HPC) thermal-hydraulic engine for Computational Fluid Dynamics (CFD) developed at the Department of System and Structure Modelling (DM2S) of the French Atomic Energy Commission (CEA).

The acronym TRUST stands for TRio_U Software for Thermalhydraulics. This software was originally designed for conduction, incompressible single-phase, and Low Mach Number (LMN) flows with a robust Weakly-Compressible (WC) multi-species solver. However, a huge effort has been conducted recently, and now TRUST is able to simulate real compressible multi-phase flows.

TRUST is also being progressively ported to support GPU acceleration (NVidia/AMD), using the Kokkos library.

The software is open source with a BSD license, available on GitHub via this link.

You can easily create new projects based on the TRUST platform. These projects are named BALTIK projects (Build an Application Linked to TRUST Kernel).

A bit of history: the Modular Software Named Trio_U

TRUST was born from the splitting of the Trio_U software into two pieces. Trio_U was a software brick based on the Kernel brick (which contains the equations, space discretizations, numerical schemes, parallelism, ...) and was used by other CEA applications (see Figure 1).

Figure 1: Trio_U brick software

In 2015, Trio_U was divided into two parts: TRUST and TrioCFD.

TRUST is a new platform; its name means: TRio_U Software for Thermohydraulics.
TrioCFD is an open source BALTIK project based on TRUST.

Here are some other selected BALTIK projects based on the TRUST platform (see Figure 2).

Figure 2: Selected BALTIK projects based on the TRUST platform.

Short History

TRUST is developed at the Laboratory of High Performance Computing and Numerical Analysis (LCAN) of the Software Engineering and Simulation Service (SGLS) in the Department of System and Structure Modeling (DM2S).

The project started in 1994 and improved versions have been built ever since:

1994: Start of the project Trio_U
1997: v1.0 - Finite Difference Volume (VDF) method only
1998: v1.1 - Finite Element Volume (VEF) method only
2000: v1.2 - Parallel MPI version
2001: v1.3 - Radiation model (TrioCFD now)
2002: v1.4 - LES turbulence models (TrioCFD now)
2006: v1.5 - VDF/VEF Front Tracking method (TrioCFD now)
2009: v1.6 - Data structure revamped
2015: v1.7 - Separation TRUST & TrioCFD + switch to open source
2019: v1.8 - New polyhedral discretization (PolyMAC) + Multiphase problem + Weakly Compressible model
2022: v1.9.0 - Modern C++ code (templates, CRTP, ...) + remove MACROS + support GPU (NVidia/AMD)
2025: v1.9.6 - Unified version to handle 32-64b integers + VEF discretization supported on GPU

Where to go next

The rest of the General Guide walks through the practical steps of writing and running a simulation:

How to use a data file — anatomy of a .data file: blocks, objects, interpretors, and how to launch it
Problem types — choosing a problem type (hydraulic, thermohydraulic, multiphase, ...)
Boundary conditions — boundary conditions
Solvers and Preconditioners — pressure solvers
Temporal schemes — time integration schemes
Spatial schemes — spatial discretization schemes
Post-Processing — output files and post-processing
Stop and restart — Solve, stop file, save and restart
Parallel Simulations — partitioning and parallel execution

For step-by-step worked examples, see the User Tutorials.

TRUST command-line reference

The trust script wraps the actual TRUST executable with a collection of convenience options. Run trust -h at any time for the live list — the groups below are a quick overview.

Information

Flag	What it does
-help, -h	List every option.
-index	Open the TRUST resource index.

Project scaffolding

Flag	What it does
-baltik [name]	Instantiate an empty baltik project.
-eclipse-trust	Generate Eclipse config to import TRUST sources.
-eclipse-baltik	Generate Eclipse config to import baltik sources (requires TRUST to have been configured under Eclipse first).

Data-file authoring

Flag	What it does
-config nedit\\|vim\\|emacs\\|gedit	Set up your editor to syntax-highlight TRUST keywords.
-edit	Edit the data file.
-jupyter	Create a basic Jupyter notebook file.
-copy	Copy a test-case data file from the TRUST database into the current directory.
-search KEYWORDS	List test cases from the database that contain the given keywords.

Mesh & parallel

Flag	What it does
-partition	Partition the mesh (creates the .Zones files).
-mesh	Visualise the mesh(es) referenced by the data file.
-c NCPUS	Use NCPUS CPUs per task for a parallel calculation.

Run monitoring & cleanup

Flag	What it does
-evol	Monitor the calculation in a GUI.
-probes	Monitor probes only.
-clean	Remove every file TRUST generated in the current directory.

Non-regression testing

Flag	What it does
-check all\\|TESTCASE\\|LISTFILE	Run non-regression checks.
-ctest all\\|TESTCASE\\|LISTFILE	Same, via the CTest harness.
-check function\\|class\\|class::method	Check the tests covering a given function, class, or method.
-ctest function\\|class\\|class::method	Same, via CTest.

Debugging & profiling

Flag	What it does
-gdb	Run under gdb.
-valgrind	Run under valgrind.
-valgrind_strict	Run under valgrind with no suppressions.
-callgrind	Run the callgrind profiler (via valgrind).
-massif	Run the massif heap profiler (via valgrind).
-heaptrack	Run heaptrack (heap profile; faster than massif).
-advisor	Run Intel Advisor (vectorisation analysis).
-vtune	Run Intel VTune (profiling).
-perf	Run Linux perf (profiling).
-trace	Run the Intel Trace Analyzer (MPI profiling).

Cluster submission

Flag	What it does
-create_sub_file	Just create a submission file, don't submit.
-prod	Create and submit on the main production queue with exclusive resource.
-bigmem	Create and submit on the big-memory production queue.
-queue QUEUE	Create and submit to a specific queue.

Passing options through to the underlying executable

Flag	What it does
datafile -help_trust	Print the options of the underlying TRUST_EXECUTABLE [CASE[.data]] [options].