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Laboratoire d'Informatique, de Robotique et de Microélectronique de Montpellier

Academic institutioneurope · fr
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Research library82linked papers
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Selected work

Representative Papers

A 3D particle visualization system for temperature management

Jan 23, 2011Electronic imaging

This paper addresses the challenge of real-time visualization and energy-efficiency analysis for massive sensor data (temperature, humidity, pressure) in data centers. To this end, we propose an adaptive particle-based modeling method tailored for thermal-field sensing. Built upon a client-server architecture, the approach integrates an enhanced Level-of-Detail (LOD) multi-scale simplification strategy—extending Clark’s 1976 theory—and pioneers the synergistic use of particle systems with dynamic detail control for data center thermal management. The system achieves millisecond-level, three-dimensional streaming rendering of tens of thousands of sensor streams, improving frame rate by 3.2×. It significantly enhances hotspot localization accuracy and accelerates energy-efficiency regulation response. As a result, it establishes a scalable, real-time thermal-state visualization paradigm for green data centers.

22 citations1 influentialRead paper

Direct Access for Conjunctive Queries with Negation

Oct 24, 2023International Conference on Database Theory

This paper investigates the direct access problem to the k-th answer in lexicographic order for conjunctive queries with negation (CQ¬) over databases: after polynomial-time preprocessing, arbitrary rank-k queries must be answered in polylogarithmic time. To address this, we systematically extend the characterization of direct-access tractability from positive conjunctive queries to CQ¬, introducing a unified framework based on representable relation circuits. We prove that both β-acyclic and bounded nested set-width classes of negative queries are tractable within this framework, strictly generalizing prior tractability boundaries for positive and negative queries. Experimental evaluation confirms that our approach achieves polynomial preprocessing and polylogarithmic access time, subsuming all previously known tractable classes and extending beyond them.

6 citations1 influentialRead paper

Approximating branchwidth on parametric extensions of planarity

Apr 10, 2023International Workshop on Graph-Theoretic Concepts in Computer Science

This paper addresses the branchwidth approximation problem for graph classes excluding two fixed graphs $H_1$ and $H_2$, each embeddable on the torus or the projective plane. For this broad family of non-planar graphs, we extend the Seymour–Thomas Ratcatcher algorithm—previously applicable only to planar graphs—to handle toroidal and projective-planar forbidden minors. Our method integrates the Graph Minor Structure Theorem, extraction of planar subgraphs, and constructive tree decomposition. The resulting algorithm runs in $O(|V|^3)$ time and achieves a constant additive approximation guarantee: the error depends solely on $H_1$ and $H_2$, not on the input graph size. This work overcomes a fundamental bottleneck—the intractability of exact branchwidth computation beyond planar graphs—and provides the first polynomial-time constant-additive approximation algorithm for branchwidth with rigorous theoretical guarantees on a wide class of non-planar graphs.

2 citationsRead paper
Recent publications

Latest Papers

A General Sufficient Condition for Rewriting Horn-ALCHI Atomic Queries into GQL

Aug 05, 2026

This work addresses the problem of efficiently rewriting atomic queries over Horn-ALCHI ontologies into UC2RPQ, a core fragment of the ISO graph query language GQL. To this end, the paper introduces a novel automata-based formal semantics for description logics and incorporates a state stratification condition to eliminate cyclic dependencies. The proposed approach establishes, for the first time, sufficient conditions under which atomic queries over Horn-ALCHI ontologies are rewritable into UC2RPQ. This result substantially extends the applicability of GQL in ontology-mediated querying and provides both a theoretical foundation and a practical pathway for the efficient evaluation of complex ontology-based queries in graph databases.

0 citationsRead paper

Lexicographic Direct Access with Functional Dependencies

Jul 15, 2026

This study investigates the complexity of achieving lexicographic direct access to join query results over databases satisfying functional dependencies (FDs). It analyzes the trade-off between preprocessing time and access efficiency through two approaches: a streamlined method based on reordered extensions and a refined technique that explicitly leverages FDs within query decomposition while incorporating information-theoretic size bounds. The work demonstrates that reordering significantly reduces complexity and provides the first complete characterization of the feasibility boundary for lexicographic direct access under linear preprocessing. Technically, it integrates FD inference, query decomposition, information-theoretic bound estimation, and fine-grained complexity analysis grounded in the Zero-Clique conjecture. Tight upper and lower bounds are established for unary FDs, and although the bounds for general FDs are not fully tight, a complete classification is achieved under the linear preprocessing regime.

0 citationsRead paper