Variable locale

Résumé

En programmation informatique, une variable locale est une variable qui ne peut être utilisée que dans la fonction ou le bloc où elle est définie. La variable locale s'oppose à la variable globale qui peut être utilisée dans tout le programme. Selon le langage utilisé, une variable locale à une fonction sera accessible ou non aux fonctions que celle-ci appelle (notion de portée d'une variable ; voir aussi la notion de « fief » en Algol 68). Types de variables dites locales Il existe deux types de variables dites locales :

une variable à déclaration locale qui est accessible à un ensemble de programmes, mais pas aux autres programmes, même si elle continue à exister ; on les trouve dans des langages à imbrications déclaratives de fonctions comme Algol et PL/I ;
une variable locale proprement dite qui est déclarée à l'intérieur d'une fonction ; elle est alors allouée sur la pile d'exécution.

Exemple en C++ void swap(auto& a, auto& b) // échange les valeu

Source officielle

https://fr.wikipedia.org/wiki/Variable_locale

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Concepts associés (19)

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Cours associés (17)

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Séances de cours associées (45)

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Scalable join processing in a parallel shared-nothing environment requires a partitioning policy that evenly distributes the processing load while minimizing the size of state maintained and number of messages communicated. Previous research proposes static partitioning schemes that require statistics beforehand. In an online or streaming environment in which no statistics about the workload are known, traditional static approaches perform poorly. This paper presents a novel parallel online dataflow join operator that supports arbitrary join predicates. The proposed operator continuously adjusts itself to the data dynamics through adaptive dataflow routing and state repartitioning. The operator is resilient to data skew, maintains high throughput rates, avoids blocking behavior during state repartitioning, takes an eventual consistency approach for maintaining its local state, and behaves strongly consistently as a black-box dataflow operator. We prove that the operator ensures a constant competitive ratio 3.75 in data distribution optimality and that the cost of processing an input tuple is amortized constant, taking into account adaptivity costs. Our evaluation demonstrates that our operator outperforms the state-of-the-art static partitioning schemes in resource utilization, throughput, and execution time.

VLDB2014

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Global Free-Energy Landscapes as a Smoothly Joined Collection of Local Maps

Michele Ceriotti, Federico Giberti, Gareth Aneurin Tribello

Enhanced sampling techniques have become an essential tool in computational chemistry and physics, where they are applied to sample activated processes that occur on a time scale that is inaccessible to conventional simulations. Despite their popularity, it is well known that they have constraints that hinder their application to complex problems. The core issue lies in the need to describe the system using a small number of collective variables (CVs). Any slow degree of freedom that is not properly described by the chosen CVs will hinder sampling efficiency. However, the exploration of configuration space is also hampered by including variables that are not relevant for the activated process under study. This paper presents the Adaptive Topography of Landscape for Accelerated Sampling (ATLAS), a new biasing method capable of working with many CVs. The root idea of ATLAS is to apply a divide-and-conquer strategy, where the high-dimensional CVs space is divided into basins, each of which is described by an automatically determined, low-dimensional set of variables. A well-tempered metadynamics-like bias is constructed as a function of these local variables. Indicator functions associated with the basins switch on and off the local biases so that the sampling is performed on a collection of low-dimensional CV spaces that are smoothly combined to generate an effectively high-dimensional bias. The unbiased Boltzmann distribution is recovered through reweighing, making the evaluation of conformational and thermodynamic properties straightforward. The decomposition of the free-energy landscape in local basins can be updated iteratively as the simulation discovers new (meta)stable states.

AMER CHEMICAL SOC2021

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Theory of inelastic light scattering in spin-1 systems: Resonant regimes and detection of quadrupolar order

Frédéric Alexis Michaud, Frédéric Mila, François Vernay

Motivated by the lack of an obvious spectroscopic probe to investigate nonconventional order such as quadrupolar orders in spin S > 1/2 systems, we present a theoretical approach to inelastic light scattering for spin-1 quantum magnets in the context of a two-band Hubbard model. In contrast to the S = 1/2 case, where the only type of local excited state is a doubly occupied state of energy U, several local excited states with occupation up to four electrons are present. As a consequence, we show that two distinct resonating scattering regimes can be accessed depending on the incident photon energy. For (h) over bar omega(in) less than or similar to U, the standard Loudon-Fleury operator remains the leading term of the expansion as in the spin-1/2 case. For (h) over bar omega(in) less than or similar to 4U, a second resonant regime is found with a leading term that takes the form of a biquadratic coupling similar to(S-i . S-j)(2). Consequences for the Raman spectra of S = 1 magnets with magnetic or quadrupolar order are discussed. Raman scattering appears to be a powerful probe of quadrupolar order.

2011

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