Publications SISSA

Pubblicazione

Performance Analysis and GPU Scalability of OGSTM-BFM

(SISSA, 2026-03-27)

FEITOSA BENEVIDES, ANDRE'

OGSTM-BFM is a coupled physical-biogeochemical model developed at the National Institute of Oceanography and Applied Geophysics (OGS) [1, 2, 3, 4] and is used for climate-related studies. Recent work within ESiWACE3 (Centre of Excellence in Simulation of Weather and Climate in Europe) reported substantial performance gains after porting the model to GPU architectures [5]. This thesis presents a reproducibility study of selected GPU performance results of OGSTM-BFM on the Leonardo supercomputer, as well as further investigations that were not included in previous ESiWACE3 reports. A signi cant acceleration can be achieved when using GPUs, provided that appropriate MPI rank-to-GPU mappings and Multi-Process Service (MPS) con gurations are employed. Several con gurations were tested. When we consider the GPU version running on two nodes, with four NVIDIA A100 GPUs per node and four MPI ranks per GPU, compared to two dual-socket nodes with Intel Sapphire Rapids CPUs, this leads to a speedup of 1.64. Once MPS is enabled, performance increases dramatically (speedup of 5.72). Di erent mappings of the ranks to the GPUs were tested. It was found that round-robin mapping combined with 50% MPS (each rank limited to ∼ 50% GPU threads), further increases the speedup to 5.97. Lastly, after adding NUMA binding in the MPS launch path, we managed to achieve a speedup of 6.22. We note that a speedup of 7.41 was reported on the ESiWACE3 Technical Report [5]; however, in this study, we were not able to actually reach this result. In addition, this work evaluates an alternative implementation of the vertical dif fusion tridiagonal solver using NVIDIA's cuSPARSE batched routines. The original implementation solved a system with a tridiagonal matrix by a method that does not allow for full parallelism. The algorithm, however, is highly specialized to tridi agonal matrices. We developed benchmark tests both in isolation and integrated into OGSTM-BFM. The cuSPARSE-based variant in isolation is about 3.33 times slower than the specialized version. When integrated into OGSTM-BFM it leads to 8% slower runs than the baseline in the tested con guration. These results emphasize that increased parallelism alone does not guarantee im proved time-to-solution; they also show that launch-level tuning (MPS, mapping, NUMAplacement) is as important as kernel-level optimization. The thesis provides practical insights into GPU reproducibility, solver integration, and performance en gineering for large-scale scienti c applications.

Pubblicazione

Gravitational waves and Black Hole perturbations in acoustic analogues

( 2025)

Coviello C.

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Chiofalo M. L.

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Grasso D.

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Liberati S.

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Mannarelli M.

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Trabucco S.

Phonons in Bose-Einstein condensates propagate as massless scalar particles on top of an emergent acoustic metric. This hydrodynamics/gravity analogy can be exploited to realize acoustic black holes, featuring an event horizon that traps phonons. The authors show that by an appropriate external potential, gravitational wave-like perturbations of the acoustic metric can be produced. Such perturbations can be used to excite an acoustic black hole, which should then relax by phonon emission.

Pubblicazione

Le ombre dell'oceano

(SISSA, 2026-03-25)

OLIVERO, GIULIA

Raccontare la conservazione di una specie significa confrontarsi con una rete di relazioni che va ben oltre la dimensione biologica. Nel caso dello squalo balena (Rhincodon typus) a Nosy Be, in Madagascar, la tutela della specie si intreccia con pratiche turistiche, tradizioni locali e dinamiche economiche, dando origine a un sistema complesso che non può essere compreso né affrontato isolando un singolo fattore. Il prodotto di tesi consiste in un podcast intitolato Le ombre dell’oceano, dedicato al rapporto ambivalente tra lo squalo balena e il turismo, con particolare attenzione alle attività di osservazione legate alla presenza stagionale della specie nell’area di Nosy Be. Il progetto prende avvio da un dato biologico ed ecologico centrale: secondo l’ultimo report dell’IUCN, pubblicato nel marzo 2025, lo squalo balena è classificato come specie a rischio. In questo contesto, Nosy Be assume un ruolo particolarmente rilevante, poiché rappresenta uno dei principali siti di aggregazione stabile e prolungata per giovani maschi. Si tratta di una fase delicata del ciclo vitale della specie, che conferisce all’area un valore strategico per la conservazione, la ricerca scientifica e lo sviluppo del turismo naturalistico. La contestualizzazione del racconto risulta quindi essenziale. Il Madagascar è un Paese in cui le tradizioni culturali e spirituali rivestono ancora un ruolo centrale nella vita quotidiana; partire dallo sguardo delle comunità locali è indispensabile per comprendere non solo la biologia dello squalo balena, ma anche il significato che la sua presenza assume e il modo in cui il turismo si inserisce in questo equilibrio. Lo squalo balena diventa così il filo conduttore per raccontare una tensione costante tra conservazione della biodiversità, rispetto delle tradizioni locali e sviluppo economico in uno dei Paesi più poveri al mondo. Il podcast si articola su quattro livelli di lettura interconnessi. Il primo livello è culturale e tradizionale e approfondisce la figura del marukintana e il sistema dei fady, attraverso la voce di Romeo. Il secondo è scientifico ed è affidato al contributo di Elena Zanella, biologa marina, che affronta la biologia, l’ecologia, lo stato di conservazione e le principali minacce per la specie. Il terzo livello è socio-economico e analizza il turismo come pratica ambivalente, capace di generare opportunità, favorire scambi culturali, creare nuove forme di lavoro e sostenere la ricerca, ma anche di esercitare pressioni significative su ecosistemi fragili in una delle aree più biodiverse del pianeta. Il quarto livello è infine etico e accompagna l’ascoltatore verso una riflessione più ampia sulle responsabilità individuali e collettive legate alle scelte di viaggio e di consumo.

Pubblicazione

Towards Quantum Advantage in Financial Market Risk using Quantum Gradient Algorithms

( 2022)

Stamatopoulos N.

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Mazzola G.

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Woerner S.

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Zeng W. J.

We introduce a quantum algorithm to compute the market risk of financial derivatives. Previous work has shown that quantum amplitude estimation can accelerate derivative pricing quadratically in the target error and we extend this to a quadratic error scaling advantage in market risk computation. We show that employing quantum gradient estimation algorithms can deliver a further quadratic advantage in the number of the associated market sensitivities, usually called greeks. By numerically simulating the quantum gradient estimation algorithms on financial derivatives of practical interest, we demonstrate that not only can we successfully estimate the greeks in the examples studied, but that the resource requirements can be significantly lower in practice than what is expected by theoretical complexity bounds. This additional advantage in the computation of financial market risk lowers the estimated logical clock rate required for financial quantum advantage from Chakrabarti et al. [Quantum 5, 463 (2021)] by a factor of ∼ 7, from 50MHz to 7MHz, even for a modest number of greeks by industry standards (four). Moreover, we show that if we have access to enough resources, the quantum algorithm can be parallelized across up to 60 QPUs, in which case the logical clock rate of each device required to achieve the same overall runtime as the serial execution would be ∼ 100kHz. Throughout this work, we summarize and compare several different combinations of quantum and classical approaches that could be used for computing the market risk of financial derivatives.

Pubblicazione

Measuring Full Counting Statistics in a Trapped-Ion Quantum Simulator

( 2025)

Joshi, Lata Kh

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Ares, Filiberto

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Joshi, Manoj K.

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Roos, Christian F.

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Calabrese, Pasquale

In quantum mechanics, the probability distribution function and full counting statistics play a fundamental role in characterizing the fluctuations of quantum observables, as they encode the complete information about these fluctuations. In this Letter, we measure these two quantities in a trapped-ion quantum simulator for the transverse and longitudinal magnetization within a subsystem. We utilize the toolbox of classical shadows to postprocess the measurements performed in random bases. The measurement scheme efficiently allows access to the full counting statistics and probability distribution function of all possible operators on desired choices of subsystems of an extended quantum system.

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