The SeaHorn Verification Framework

In this paper, we present SeaHorn, a software verification framework. The key distinguishing feature of SeaHorn is its modular design that separates the concerns of the syntax of the programming language, its operational semantics, and the verification semantics. SeaHorn encompasses several novelties: it (a) encodes verification conditions using an efficient yet precise inter-procedural technique, (b) provides flexibility in the verification semantics to allow different levels of precision, (c) leverages the state-of-the-art in software model checking and abstract interpretation for verification, and (d) uses Horn-clauses as an intermediate language to represent verification conditions which simplifies interfacing with multiple verification tools based on Horn-clauses. SeaHorn provides users with a powerful verification tool and researchers with an extensible and customizable framework for experimenting with new software verification techniques. The effectiveness and scalability of SeaHorn are demonstrated by an extensive experimental evaluation using benchmarks from SV-COMP 2015 and real avionics code

A Tool for Intersecting Context-Free Grammars and Its Applications

This paper describes a tool for intersecting context-free grammars. Since this problem is undecidable the tool follows a refinement-based approach and implements a novel refinement which is complete for regularly separable grammars. We show its effectiveness for safety verification of recursive multi-threaded programs

Diet and Leukocyte Telomere Length in a Population with Extended Longevity: The Costa Rican Longevity and Healthy Aging Study (CRELES)

Elderly Costa Ricans have lower mortality rates compared to their counterparts from developed countries. Reasons for this survival advantage are not completely known. In the present study, we aimed to identify dietary factors associated with leukocyte telomere length (LTL), a marker of biologic aging, in the elderly population of Costa Rica. We conducted prospective analysis in 909 participants aged 60+ years from the Costa Rican Longevity and Healthy Aging Study (CRELES). We used a food frequency questionnaire to assess usual diet. We calculated dietary patterns using Principal Component Analysis (PCA). We used generalized linear models to examine the association of dietary patterns and food groups with leukocyte telomere length. We found two major dietary patterns explaining 9.15% and 7.18% of the total variation of food intake, respectively. The first dietary pattern, which represents a traditional Costa Rican rice and beans pattern, was more frequent in rural parts of the country and was positively associated with baseline LTL: (95% CI) = 42.0 base-pairs (bp) (9.9 bp, 74.1 bp) per one-unit increase of the traditional dietary pattern. In analysis of individual food groups, intake of grains was positively associated with baseline LTL: (95% CI) = 43.6 bp (13.9 bp, 73.3 bp) per one-serving/day increase of consumption of grains. Our results suggest that dietary factors, in particular a traditional food pattern, are associated with telomere length and may contribute to the extended longevity of elderly Costa Ricans.Universidad de Costa Rica/[]/UCR/Costa RicaNational Institutes of Health/[P30 AG012839]/NIH/Estados UnidosNational Institutes of Health/[R01 AG031716]/NIH/Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Sociales::Centro Centroamericano de Población (CCP)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Analyzing Array Manipulating Programs by Program Transformation

We explore a transformational approach to the problem of verifying simple array-manipulating programs. Traditionally, verification of such programs requires intricate analysis machinery to reason with universally quantified statements about symbolic array segments, such as "every data item stored in the segment A[i] to A[j] is equal to the corresponding item stored in the segment B[i] to B[j]." We define a simple abstract machine which allows for set-valued variables and we show how to translate programs with array operations to array-free code for this machine. For the purpose of program analysis, the translated program remains faithful to the semantics of array manipulation. Based on our implementation in LLVM, we evaluate the approach with respect to its ability to extract useful invariants and the cost in terms of code size

The STR polymorphism (AAAAT)n within the intron 1 of the tumor protein 53 (TP53) locus in 17 populations of different ethnic groups of Africa, America, Asia and Europe

artículo arbitrado -- Universidad de Costa Rica, Instituto de investigaciones en Salud. 2004The SIR (A.AAAT). within intron 1 of the TP53 Locus was screened in 17 populations from 3 main ethnic groups: Europeans, Asiatics, and Africans. and from the hybrid population of Costa Rica (1968 samples). Three alleles, 126)7 (bp/copies of the repeat), 13118 and 136/9 were the most prevalent in all populations. Other alleles rarely reached frequencies of 10% or higher. Observed heterozygosities ranged between 0.351 and 0.829. Patterns of diversity fit well with both the geographic origin of the samples and the history of the populations screened. A statistical test suggests that single-step mutational events have been the main mechanism producing new alleles at this locus. Fixation indexes (R57) for this marker showed an effect of population subdivision on divergence only within the Asiatic group; they were insensitive at the level of major ethnic groups as well as within Africans and within EuropeansSe estudio el polimorfismo del microsatelite (AAAAI), del intron 1 del gene TP53 en 17 poblaciones de 3 grupos etnicos: europeos, asiaticos, y africanos subsaharianos, asi coma de la poblacion hibrida de Costa Rica (en total 1968 muestras). Tres aides, 12617 (pares de bases/ copias de la repetición), 131/8 y 136/9 fueron los mas frecuentes en todas las poblaciones, aunque se observaron otros alelos usualmente a frecuencias menores al 10%. Las heterocigosis observadas variaron de 0.351 a 0.829. La distribucion de la universidad parece concordar con el origen geográfico de las muestras y con la historia de las poblaciones estudiadas. Una prueba estadística indica que el evento mutacional que mas alelos nuevos produce en ese marcador es el de un solo paso (expansión o contracción de una cola copia de la repeticion). El indice de fijacion R„ mostro los efectos de la subdivision de poblaciones solo dentro del grupo de los asiaticos y mostro falta de sensibilidad cuando los grupos comparados eran de nivetes superiores de clasificacion (europeos, asiaticos, y africanos) o cuando la comparación se hizo entre los grupos mas antiguos (africanos y europeos).Universidad de costa Rica, Instituto de investigaciones en Salud.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto de Investigaciones en Salud (INISA