arXiv subjects

Davide Vanzo

Publications and source records attributed to Davide Vanzo.

6 recordsLinked to original sources

arXiv2024

Simplifying HPC resource selection: A tool for optimizing execution time and cost on Azure

Azure Cloud offers a wide range of resources for running HPC workloads, requiring users to configure their deployment by selecting VM types, number of VMs, and processes per VM. Suboptimal decisions may lead to longer execution times or additional costs for the user. We are developing an open-source tool to assist users in making these decisions by considering application input parameters, as they influence resource consumption. The tool automates the time-consuming process of setting up the cloud environment, executing the benchmarking runs, handling output, and providing users with resource selection recommendations as high level insights on run times and costs across different VM types and number of VMs. In this work, we present initial results and insights on reducing the number of cloud executions needed to provide such guidance, leveraging data analytics and optimization techniques with two well-known HPC applications: OpenFOAM and LAMMPS.

cs.DC↗

arXiv2021

BASEMENT v3: a modular freeware for river process modelling over multiple computational backends

Modelling river physical processes is of critical importance for flood protection, river management and restoration of riverine environments. Developments in algorithms and computational power have led to a wider spread of river simulation tools. However, the use of two-dimensional models can still be hindered by complexity in the setup and the high computational costs. Here we present the freeware BASEMENT version 3, a flexible tool for two-dimensional river simulations that bundles solvers for hydrodynamic, morphodynamic and scalar advection-diffusion processes. BASEMENT leverages different computational platforms (multi-core CPUs and graphics processing units GPUs) to enable the simulation of large domains and long-term river processes. The adoption of a fully costless worflow and a light GUI facilitate its broad utilization. We test its robustness and efficiency in a selection of benchmarks. Results confirm that BASEMENT could be an efficient and versatile tool for research, engineering practice and education in river modelling.

physics.flu-dyn↗

arXiv2021

A splitting scheme for the coupled Saint-Venant-Exner model

We present a splitting method for the one-dimensional Saint-Venant-Exner equations used for describing the bed evolution in shallow water systems. We adapt the flux vector splitting approach of Toro and Vazquez-Cendòn and identify one subsystem of conservative equations (advection system) and one of non-conservative equations (pressure system), both having a very simple eigenstructure compared to the full system. The final numerical scheme is constructed using a Godunov-type path-conservative scheme for the pressure system and a simple conservative Godunov method for the advection system and solved following a coupled solution strategy. The resulting first-order accurate method is extended to second order of accuracy in space and time via the ADER approach together with an AENO reconstruction technique. Accuracy, robustness and well-balanced properties of the resulting scheme are assessed through a carefully selected suite of testcases. The scheme is exceedingly simple, accurate and robust as the sophisticated Godunov methods. A distinctive feature of the novel scheme is its flexibility in the choice of the sediment transport closure formula, which makes it particularly attractive for scientific and engineering applications.

math.NA↗

arXiv2019

Mathematical study of linear morphodynamic acceleration and derivation of the MASSPEED approach

Morphological accelerators, such as the MORFAC (MORphological acceleration FACtor) approach, are widely adopted techniques for the acceleration of the bed evolution, which reduces the computational cost of morphodynamic numerical simulations. In this work we apply a non-uniform acceleration to the one-dimensional morphodynamic problem described by the de Saint Venant-Exner model by multiplying all the spatial derivatives by an individual constant (>1) acceleration factor. The final goal is to identify the best combination of the three accelerating factors for which i) the bed responds linearly to hydrodynamic changes; ii) a consistent decrease of the computational cost is obtained. The sought combination is obtained by studying the behaviour of an approximate solution of the three eigenvalues associated with the flux matrix of the accelerated system. This approach allows to derive a new linear morphodynamic acceleration technique, the MASSPEED (MASs equations SPEEDup) approach, and the a priori determination of the highest acceleration allowed for a given simulation. In this new approach both mass conservation equations (water and sediment) are accelerated by the same factor, differently from the MORFAC approach where only the sediment mass equation is modified. The analysis shows that the MASSPEED gives a larger validity range for linear acceleration and requires smaller computational costs than that of the classical MORFAC approach. The MASSPEED approach is implemented within an example code, using an adaptive approach that applies the maximum linear acceleration similarly to the Courant-Friedrichs-Lewy stability condition. Finally, numerical simulations have been performed in order to assess the accuracy and efficiency of the new approach. Results obtained in the long-term propagation of a sediment hump demonstrate the advantages of the new approach.

physics.flu-dyn↗

arXiv2018

A new class of non-identifiable skew symmetric tensors

We prove that the generic element of the fifth secant variety $σ_5(Gr(\mathbb{P}^2,\mathbb{P}^9)) \subset \mathbb{P}(\bigwedge^3 \mathbb{C}^{10})$ of the Grassmannian of planes of $\mathbb{P}^9$ has exactly two decompositions as a sum of five projective classes of decomposable skew-symmetric tensors. {We show that this, {together with $Gr(\mathbb{P}^3, \mathbb{P}^8)$, is the only non-identifiable case} among the non-defective secant varieties $σ_s(Gr(\mathbb{P}^k, \mathbb{P}^n))$ for any $n<14$. In the same range for $n$, we classify all the weakly defective and all tangentially weakly defective secant varieties of any Grassmannians.} We also show that the dual variety $(σ_3(Gr(\mathbb{P}^2,\mathbb{P}^7)))^{\vee}$ of the variety of 3-secant planes of the Grassmannian of $\mathbb{P}^2\subset \mathbb{P}^7$ is $σ_2(Gr(\mathbb{P}^2,\mathbb{P}^7))$ the variety of bi-secant lines of the same Grassmannian. The proof of this last fact has a very interesting physical interpretation in terms of measurement of the entanglement of a system of 3 identical fermions, the state of each of them belonging to a 8-th dimensional "Hilbert" space.

math.AG↗

arXiv2015

An algorithm for constructing certain differential operators in positive characteristic

Given a non-zero polynomial $f$ in a polynomial ring $R$ with coefficients in a finite field of prime characteristic $p$, we present an algorithm to compute a differential operator $δ$ which raises $1/f$ to its $p$th power. For some specific families of polynomials, we also study the level of such a differential operator $δ$, i.e., the least integer $e$ such that $δ$ is $R^{p^e}$-linear. In particular, we obtain a characterization of supersingular elliptic curves in terms of the level of the associated differential operator.

math.AC↗