tglfnn-ukaea

Neural network surrogate models of the TGLF quasilinear plasma turbulent transport simulator in various parameter spaces.

Paper for acknowledgment

If you use these models within your work, we request you cite the following paper:

• L. Zanisi et al., Data efficent digital twinning strategies and surrogate models of quasilinear turbulence in JET and STEP, International Atomic Energy Agency - Fusion Energy Conference, Chengdu, China, 2025

Usage

Various different methods exist for using the models:

1. Loading from PyTorch checkpoint
2. Loading traced ONNX model
3. Loading traced TorchScript model
4. Loading the parameters directly into pure Python

Loading the traced TorchScript model allows the model to be used in Fortran (see below). Loading the parameters directly is a minimal-dependency method designed for use with other machine learning frameworks.

1. Loading from PyTorch checkpoint

import torch

# Load the model
efe_gb_model = torch.load('MultiMachineHyper_1Aug25/regressor_efe_gb.pt')

# Call the model
input_tensor = torch.tensor([[...]], dtype=torch.float32)  # Replace with appropriate input
output_tensor = efe_gb_model(input_tensor)

2. Loading traced ONNX model

import onnxruntime as ort

# Load the model
ort_session = ort.InferenceSession('MultiMachineHyper_1Aug25/regressor_efe_gb.onnx')

# Call the model
input_tensor = np.array([[...]], dtype=np.float32)  # Replace with appropriate input
outputs = ort_session.run(None, {'input': input_tensor})

3. Loading traced TorchScript model

import torch

# Load the model
torchscript_model = torch.jit.load('MultiMachineHyper_1Aug25/regressor_efe_gb_torchscript.pt')

# Call the model
input_tensor = torch.tensor([[...]], dtype=torch.float32)  # Replace with appropriate input
output_tensor = torchscript_model(input_tensor)

Using the traced TorchScript models in Fortran

The traced PyTorch models can be used in Fortran with FTorch, which provides Fortran bindings for LibTorch (the C++ backend of PyTorch). Please cite the Ftorch publication if using these models from Fortran.

Further details on the FTorch Implementation of these networks can be found in a related project.

Prerequisites

• LibTorch: Download the appropriate version (CPU or GPU) from the PyTorch website and ensure it is accessible in your environment. CPU versions of the LibTorch and Pip packages have been tested. The LibTorch version requires no Python to install or run. It is suggested to look at the FTorch instructions below first.
• FTorch: Install the FTorch library following the instructions in the FTorch repository. This also provides a compiler specific module (ftorch.mod).
• Fortran Compiler: Use a modern Fortran compiler (e.g., gfortran or ifort) compatible with FTorch.
• CMake: Version >= 3.1 required to build FTorch. Not essential, but helpful for building final Fortran code.

4. Compare TGLF and TGLFNN in JETTO production runs

• TGLFNN is only an approximation of TGLF and it will make mistakes
• scripts/tglf_vs_nn_jetto_trajectories.py shows how to plot the inputs and outputs spanned by TGLF and TGLFNN in a JETTO production run. NOTE: Available only in the following build on the JDC /home/tn2395/jintrac-devel