OLŠÁK, O. Akcelerace výpočtů simulací šíření vln pomocí prořezané Fourierovy transformace [online]. Brno: Vysoké učení technické v Brně. Fakulta informačních technologií. 2026.
Ondřej Olšák pursued his PhD studies at the Faculty of Information Technology, Brno University of Technology, from 2021 to 2026. His research focused on the acceleration of ultrasound simulations based on k-space corrected pseudospectral methods on GPU-accelerated high-performance computing (HPC) systems. During his doctoral studies, he addressed several challenging and relevant research topics. First, he conducted an in-depth performance analysis of existing implementations of the k-Wave toolbox and identified opportunities for significant simulation acceleration, even at the cost of a carefully controlled and acceptable loss of accuracy. Second, he carried out a comprehensive review of fast Fourier transform (FFT) implementations, aiming to reduce computational costs by exploiting a priori information about the simulation in the context of modern HPC architectures. Two promising approaches, sparse FFTs and pruned FFTs, were identified and thoroughly investigated using realistic medium and transducer parameters. This research resulted in the development of a novel technique based on a pruned FFT, which reduces the computational complexity of the Fourier transform by approximately a factor of two. The technique leverages a simple and fast model, referred to as the Acoustic Field Propagator, which provides an initial estimate of the significant frequency components in the simulation. Based on this estimate, negligible parts of the spectrum are discarded. To control and quantify the error introduced by spectrum pruning, several error metrics were investigated and ultimately integrated into the final simulation toolbox. The outcomes of this work have been disseminated through four peer-reviewed conference publications, including Core A conferences (ICCS and HPDC), Core C conferences (HPCC), as well as the high-quality bioinformatics conference ICBRA. In addition, Ondřej presented his research in six poster contributions at both local conferences and international workshops. Ondřej Olšák also played a vital role in the EU Horizon Europe CITRUS project from October 2022 to September 2025. Within this project, he worked on accelerating ultrasound simulations using sparse FFT techniques and contributed to the development of a graphical user interface and a REST API for a software-as-a-service system for simulation dispatch and monitoring. He also presented the progress of the entire SC@FIT research group at the project’s annual monitoring meeting. In addition, he participated in a faculty-funded IGA project from 2023 to 2026. On the personal level, it was a pleasure to supervise Ondřej Olšák. He is a patient, well-organized, reliable, and highly self-motivated researcher. His ability to work independently, combined with excellent time management, enabled him to successfully complete his doctoral studies within four years. In summary, I wholeheartedly endorse Ondřej Olšák for the award of the doctoral degree. His exceptional enthusiasm for research, outstanding academic performance, and significant research achievements clearly demonstrate his readiness for independent work in science, research, and development. He has consistently exhibited the qualities expected of a doctoral candidate, and I firmly believe he is truly deserving of this recognition and honor.
Ondrej has published his research in four peer-reviewed conference papers at four international conferences highly-regarded in the field of computational science. Both in his published work and the thesis, Ondre provides not only a clear theoretical justification for the approach he has taken, but also a thorough explanation of the algorithm he developed, a description of its implementation, and a convincing demonstration of its performance on applications of interest. This broad span of work shows he has a very good grasp of his topic and its relevance to biomedical ultrasound. In conclusion, this doctoral thesis clearly meets the academic and scientific requirements for the award of a PhD degree.
The thesis and the student's achievements fulfill the generally accepted requirements for the award of the academic degree Doctor of Philosophy. I recommend acceptin the thesis.
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