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Accelerating linear system solvers for time domain component separation of cosmic microwave background data

Jan Papež 1 Laura Grigori 1 Radek Stompor 2, 3, 1
1 ALPINES - Algorithms and parallel tools for integrated numerical simulations
INSMI - Institut National des Sciences Mathématiques et de leurs Interactions, Inria de Paris, LJLL (UMR_7598) - Laboratoire Jacques-Louis Lions
Abstract : Component separation is one of the key stages of any modern cosmic microwave background (CMB) data analysis pipeline. It is an inherently non-linear procedure and typically involves a series of sequential solutions of linear systems with similar, albeit not identical, system matrices, derived for different data models of the same data set. Sequences of this kind arise for instance in the maximization of the data likelihood with respect to foreground parameters or sampling of their posterior distribution. However, they are also common in many other contexts. In this work we consider solving the component separation problem directly in the measurement (time) domain. This can have a number of important benefits over the more standard pixel-based methods, in particular if non-negligible time-domain noise correlations are present, as it is commonly the case. The time-domain based approach implies, however, significant computational effort due to the need to manipulate the full volume of time-domain data set. To address this challenge, we propose and study efficient solvers adapted to solving time-domain-based component separation systems and their sequences, and which are capable of capitalizing on information derived from the previous solutions. This is achieved either via adapting the initial guess of the subsequent system or through a so-called subspace recycling, which allows to construct progressively more efficient, two-level preconditioners. We report an overall speed-up over solving the systems independently of a factor of nearly 7, or 5, in our numerical experiments inspired respectively by the likelihood maximization and likelihood sampling procedures considered in this work.
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https://hal.inria.fr/hal-02470964
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Submitted on : Wednesday, April 1, 2020 - 2:02:53 PM
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Jan Papež, Laura Grigori, Radek Stompor. Accelerating linear system solvers for time domain component separation of cosmic microwave background data. 2020. ⟨hal-02470964v2⟩

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