Optimization Modulo Theories with Linear Rational Costs

In the contexts of automated reasoning (AR) and formal verification (FV), important decision problems are effectively encoded into Satisfiability Modulo Theories (SMT). In the last decade efficient SMT solvers have been developed for several theories of practical interest (e.g., linear arithmetic, arrays, bit-vectors). Surprisingly, little work has been done to extend SMT to deal with optimization problems; in particular, we are not aware of any previous work on SMT solvers able to produce solutions which minimize cost functions over arithmetical variables. This is unfortunate, since some problems of interest require this functionality. In the work described in this paper we start filling this gap. We present and discuss two general procedures for leveraging SMT to handle the minimization of linear rational cost functions, combining SMT with standard minimization techniques. We have implemented the procedures within the MathSAT SMT solver. Due to the absence of competitors in the AR, FV and SMT domains, we have experimentally evaluated our implementation against state-of-the-art tools for the domain of linear generalized disjunctive programming (LGDP), which is closest in spirit to our domain, on sets of problems which have been previously proposed as benchmarks for the latter tools. The results show that our tool is very competitive with, and often outperforms, these tools on these problems, clearly demonstrating the potential of the approach.Comment: Submitted on january 2014 to ACM Transactions on Computational Logic, currently under revision. arXiv admin note: text overlap with arXiv:1202.140

Conjectural History vs. the Bible: Eighteenth-Century Scottish Historians and the Idea of History in the Encyclopaedia Britannica

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Optimization in SMT with LA(Q) Cost Functions

In the contexts of automated reasoning and formal verification, important decision problems are effectively encoded into Satisfiability Modulo Theories (SMT). In the last decade efficient SMT solvers have been developed for several theories of practical interest (e.g., linear arithmetic, arrays, bit-vectors). Surprisingly, very few work has been done to extend SMT to deal with optimization problems; in particular, we are not aware of any work on SMT solvers able to produce solutions which minimize cost functions over arithmetical variables. This is unfortunate, since some problems of interest require this functionality. In this paper we start filling this gap. We present and discuss two general procedures for leveraging SMT to handle the minimization of LA(Q) cost functions, combining SMT with standard minimization techniques. We have implemented the proposed approach within the MathSAT SMT solver. Due to the lack of competitors in AR and SMT domains, we experimentally evaluated our implementation against state-of-the-art tools for the domain of linear generalized disjunctive programming (LGDP), which is closest in spirit to our domain, on sets of problems which have been previously proposed as benchmarks for the latter tools. The results show that our tool is very competitive with, and often outperforms, these tools on these problems, clearly demonstrating the potential of the approach.Comment: A shorter version is currently under submissio

Physiological and molecular aspects of the melon-Fusarium oxysporum f. sp. melonis race 1.2 pathosystem

Fusarium oxysporum f.sp. melonis race 1.2 (FOM1.2) is the most virulent and yield-limiting pathogen of melon (Cucumis melo L.) cultivation worldwide. Colonization of plants by FOM leads to necrosis of the infected tissues, collapse of vascular vessels and decay of the plant. Resistance to FOM1.2 appears to be controlled by multiple recessive genes and strongly affected by environment. A RNA-Sequencing approach was used to investigate the transcriptome dynamic during incompatible and compatible interactions for the identification of candidate resistance genes in the melon-FOM1.2 pathosystem. The doubled-haploid (DH) resistant line NAD and the susceptible cultivar Charentais-T (CHT), both inoculated with FOM1.2, were analyzed at 24 and 48 hours post-inoculation (hpi). The landscape of differentially expressed genes (DEGs) diverged significantly in the two genotypes. Transcriptome analysis of NAD identified 2461 and 821 DEGs (82% up-regulated at 24 hpi and 69% at 48 hpi), while in CHT 882 and 2237 DEGs were recovered at 24 hpi and at 48 hpi, respectively (29% up-regulated at 24 hpi and 81% at 48 hpi). Several unannotated transcripts were found to be modulated, providing a basis for further exploration of plant defense-related genes. NAD, unlike CHT, modulates a higher proportion of up-regulated genes at 24 hpi, suggesting a more prompt response. Gene ontology (GO) enrichment of DEGs highlighted that ″defence response, incompatible interaction″ and ″response to stress″ GO groups emerged as major effectors of NAD resistance to FOM1.2. Both constitutive and inducible defense responses contribute to reduced FOM1.2 vascular colonization of melon resistant genotype. Of particular interest were transcripts involved in the cell wall reinforcement and disease resistance genes including FMO1, E3 Ubiquitin protein ligase and pathogenesis-related thaumatin encoding genes. Although the early expression of ankyrin-repeat containing genes, probably related to salicylic acid (SA) pathway, in NAD FOM1.2 resistance seems mainly mediated by the crosstalk among jasmonate/ethylene (JA/ET), auxin and abscissic acid (ABA) hormone signaling networks. Fungal transcripts expressed in planta were also detected for identifying potential virulence effectors. The achievement of candidate resistance genes and the identification of unique melon sequences with unknown functions required the establishment of efficient, genotype-specific melon regeneration and transformation protocols for future functional genomics studies. Three cultivars (CHT, Vedrantais and Isabelle) and three DH melon lines (NAD, DH-L2 and DH-L6) were tested for their potential to regenerate under in vitro conditions. The results confirmed that the hormonal requirement and the genotype strongly influence plant regeneration in melon. In order to confirm genetic stability of the regenerated melon plants a PCR-based Random Amplified Polymorphic DNA (RAPD) analysis was carried out using 20 decamer-primers

L’Atlantique des Lumières. Race, genre, histoire

Silvia Sebastiani, maîtresse de conférences L’Atlantique des Lumières : écritures de l’histoire, divisions humaines et cartographies des races Dans le prolongement du séminaire co-organisé avec Alice Ingold sur « Géographies de la nature : empires et environnement (XVIIIe-XIXe siècle) », les séances sur « l’Atlantique des Lumières » ont cherché à développer à travers des approches et des matériaux variés, la question de l’écriture de l’« histoire » du Nouveau Monde au siècle des Lumières. Not..

Administrer les « ressources naturelles », XIXe-XXe siècles

Alice Ingold, Silvia Sebastiani, maîtres de conférences Géographies de la nature : empires et environnement (XVIIIe-XIXe siècles) Les rapports entre empires et environnement ont généralement été analysés sous l’angle du bilan écologique des colonisations, au travers des modalités d’exploitation de la nature mais aussi des politiques de conservation de l’environnement, pour lesquelles les horizons impériaux ont souvent été des bancs d’épreuve. En ouvrant chronologiquement l’enquête à la périod..

Administrer les « ressources naturelles », XIXe-XXe siècles

Alice Ingold, Silvia Sebastiani, maîtres de conférences Géographies de la nature : empires et environnement (XVIIIe-XIXe siècles) Les rapports entre empires et environnement ont généralement été analysés sous l’angle du bilan écologique des colonisations, au travers des modalités d’exploitation de la nature mais aussi des politiques de conservation de l’environnement, pour lesquelles les horizons impériaux ont souvent été des bancs d’épreuve. En ouvrant chronologiquement l’enquête à la périod..

Forum: Closeness and Distance in the Age of Enlightenment Introduction

According to Michel de Certeau, distance is the indispensable prerequisite for historical knowledge and the very characteristic of modern historiography. The historian speaks, in the present, about the absent, the dead, as Certeau labels the past, thus emphasizing the performative dimension of historical writing: “the function of language is to introduce through saying what can no longer be done.” As a consequence, the heterogeneity of two non-communicating temporalities becomes the challenge to be faced: the present of the historian, as a moment du savoir, is radically separated from the past, which exists only as an objet de savoir, the meaning of which can be restored by an operation of distantiation and contextualization. In Evidence de l’histoire: Ce que voient les historiens, François Hartog takes up the question of history writing and what is visible, or more precisely the modalities historians have employed to narrate the past, opening up the way to a reflection on the boundaries between the visible and the invisible: the mechanisms that have contributed to establish these boundaries over time, and the questions that have legitimized the survey of what has been seen or not seen. But, as Mark Phillips points out, it is the very ubiquity of the trope of distance in historical writings that has paradoxically rendered it almost invisible to historians, so that “it has become difficult to distinguish between the concept of historical distance and the idea of history itself.