The MICROCARD project has brought its main achievement, a code for macroscopic cell-by-cell simulation of cardiac electrophysiology, to near completion. It has thus helped to move the state of the art in cardiac simulation from homogenized models to models in which individual cells are represented.
The project has further produced building blocks for this code which in themselves represent advances in the state of the art in different domains. We designed and implemented a novel approach to run simulations with solution-adapted resolution, which reduces the computational workload by a factor up to eight. This is usually not achieved with traditional mesh refinement and coarsening. We enhanced the widely used openCARP simulation code with strongly accelerated membrane models for both CPU and GPU platforms, thanks to a dedicated model compiler based on the MLIR/LLVM framework. We further provided openCARP with asynchronous output, GPU support for linear algebra, and support for deployment and for the sharing of experiment designs. We implemented several new algorithms in the Ginkgo linear algebra library, bringing GPU support to our code but also to other software. We robustified the mmg3d software, so that it can reliably process our meshes with numerous and tighthly apposed internal boundaries. This progress benefits other applications as well, from biomedical to aeronautics. We also implemented new functionality in the ParMmg code, the parallel cousin of mmg3d. Finally, we developed a completely new code to produce artificial cardiac tissue meshes.
By the end of the project there was still no exascale supercomputer available for research in Europe, and our code was also not entirely ready to run on it. However, a working code was completed a month after the project, and will be further tested and developed by the Centre of Excellence (CoE) MICROCARD-2, which started in November 2024. The CoE will also continue to improve solver and preconditioner algorithms, and code to create artificial tissue meshes, to allow large-scale testing.
In summary, the MICROCARD project has helped one important application, simulation of the heart, to benefit from exascale machines. We expect that this will also help related fields, such as brain research, to make better use of future exascale supercomputers. Some of our work, e.g. in Ginkgo and in Mmg, will even benefit areas of research very far from ours. The tools that MICROCARD has developed will soon be usable for cardiology research and will allow a vast array of urgent questions to be answered, leading to a better understanding and diagnosis of cardiac arrhythmia.
