arXiv subjects

S. Bertocco

Publications and source records attributed to S. Bertocco.

24 records · Page 2Linked to original sources

arXiv2022

BeyondPlanck VIII. Efficient Sidelobe Convolution and Correction through Spin Harmonics

We introduce a new formulation of the Conviqt convolution algorithm in terms of spin harmonics, and apply this to the problem of sidelobe correction for BeyondPlanck, the first end-to-end Bayesian Gibbs sampling framework for CMB analysis. We compare our implementation to the previous Planck LevelS implementation, and find good agreement between the two codes in terms of accuracy, but with a speed-up reaching a factor of 3--10, depending on the frequency bandlimits, $l_{\textrm{max}}$ and $m_{\textrm{max}}$. The new algorithm is significantly simpler to implement and maintain, since all low-level calculations are handled through an external spherical harmonic transform library. We find that our mean sidelobe estimates for Planck LFI agree well with previous efforts. Additionally, we present novel sidelobe rms maps that quantify the uncertainty in the sidelobe corrections due to variations in the sky model.

astro-ph.CO↗

arXiv2020

BeyondPlanck II. CMB map-making through Gibbs sampling

We present a Gibbs sampling solution to the map-making problem for CMB measurements, building on existing destriping methodology. Gibbs sampling breaks the computationally heavy destriping problem into two separate steps; noise filtering and map binning. Considered as two separate steps, both are computationally much cheaper than solving the combined problem. This provides a huge performance benefit as compared to traditional methods, and allows us for the first time to bring the destriping baseline length to a single sample. We apply the Gibbs procedure to simulated Planck 30 GHz data. We find that gaps in the time-ordered data are handled efficiently by filling them with simulated noise as part of the Gibbs process. The Gibbs procedure yields a chain of map samples, from which we may compute the posterior mean as a best-estimate map. The variation in the chain provides information on the correlated residual noise, without need to construct a full noise covariance matrix. However, if only a single maximum-likelihood frequency map estimate is required, we find that traditional conjugate gradient solvers converge much faster than a Gibbs sampler in terms of total number of iterations. The conceptual advantages of the Gibbs sampling approach lies in statistically well-defined error propagation and systematic error correction, and this methodology forms the conceptual basis for the map-making algorithm employed in the BeyondPlanck framework, which implements the first end-to-end Bayesian analysis pipeline for CMB observations.

astro-ph.CO↗

arXiv2019

INAF Trieste Astronomical Observatory Information Technology Framework

INAF Trieste Astronomical Observatory (OATs) has a long tradition in information technology applied to Astronomical and Astrophysical use cases, particularly for what regards computing for data reduction, analysis and simulations; data and archives management; space missions data processing; design and software development for ground-based instruments. The ensemble of these activities, in the last years, pushed the need to acquire new computing resources and technologies and to deep competences in theirs management. In this paper we describe INAF-OATs computing centre technological stuff, our involvement in different EU Projects both in the path of building of EOSC, the European Open Science Cloud; in the design and prototyping of new Exascale supercomputers in Europe and the main research activities carried on using our computing centre.

astro-ph.IM↗

arXiv2019

Direct N-body application on low-power and energy-efficient parallel architectures

The aim of this work is to quantitatively evaluate the impact of computation on the energy consumption on ARM MPSoC platforms, exploiting CPUs, embedded GPUs and FPGAs. One of them possibly represents the future of High Performance Computing systems: a prototype of an Exascale supercomputer. Performance and energy measurements are made using a state-of-the-art direct $N$-body code from the astrophysical domain. We provide a comparison of the time-to-solution and energy delay product metrics, for different software configurations. We have shown that FPGA technologies can be used for application kernel acceleration and are emerging as a promising alternative to "traditional" technologies for HPC, which purely focus on peak-performance than on power-efficiency.

cs.PF↗

arXiv2018

Cloud access to interoperable IVOA-compliant VOSpace storage

Handling, processing and archiving the huge amount of data produced by the new generation of experiments and instruments in Astronomy and Astrophysics are among the more exciting challenges to address in designing the future data management infrastructures and computing services. We investigated the feasibility of a data management and computation infrastructure, available world-wide, with the aim of merging the FAIR (Findable, Accessible, Interoperable, Reusable) data management provided by IVOA standards with the efficiency and reliability of a cloud approach. Our work involved the Canadian Advanced Network for Astronomy Research (CANFAR) infrastructure and the European EGI federated cloud (EFC). We designed and deployed a pilot data management and computation infrastructure that provides IVOA-compliant VOSpace storage resources and wide access to interoperable federated clouds. In this paper, we detail the main user requirements covered, the technical choices and the implemented solutions and we describe the resulting Hybrid cloud Worldwide infrastructure, its benefits and limitations.

astro-ph.IM↗

arXiv2001

A slow control system for the Garfield apparatus

The major part of the GARFIELD apparatus electronics are monitored and set up through a slow control system, which has been developed at LNL. A software package based on Lab View has been dedicated to the setting and control of 16 channels integrated Amplifiers and Constant Fraction Discriminators. GPIB controllers and GPIB-ENET interfaces have been used for the communication between the Personal Computer and the front-end of the electronics.

nucl-ex↗