An SMT-Based Concolic Testing Tool for Logic Programs

[EN] Concolic testing combines symbolic and concrete execution to generate test cases that achieve a good program coverage. Its benefits have been demonstrated for more than 15 years in the case of imperative programs. In this work, we present a concolic-based test generation tool for logic programs which exploits SMT-solving for constraint resolutionThird author is a research associate at FNRS that also supports this work (O05518FRG03). The last author is partially supported by the EU (FEDER) and the Spanish MCI/AEI under grants TIN2016-76843-C4-1-R/PID2019-104735RB-C41 and by the Generalitat Valenciana under grant Prometeo/2019/098 (DeepTrust)Fortz, S.; Mesnard, F.; Payet, E.; Perrouin, G.; Vanhoof, W.; Vidal, G. (2020). An SMT-Based Concolic Testing Tool for Logic Programs. Springer Nature. 215-219. https://doi.org/10.1007/978-3-030-59025-3_13S215219de Moura, L., Bjørner, N.: Z3: an efficient SMT solver. In: Ramakrishnan, C.R., Rehof, J. (eds.) TACAS 2008. LNCS, vol. 4963, pp. 337–340. Springer, Heidelberg (2008). https://doi.org/10.1007/978-3-540-78800-3_24Giantsios, A., Papaspyrou, N., Sagonas, K.: Concolic testing for functional languages. Sci. Comput. Program. 147, 109–134 (2017)Godefroid, P., Klarlund, N., Sen, K.: DART: directed automated random testing. In: Proceedings of PLDI 2005, pp. 213–223. ACM (2005)Mesnard, F., Payet, É., Vidal, G.: Concolic testing in logic programming. TPLP 15(4–5), 711–725 (2015). https://doi.org/10.1017/S1471068415000332Mesnard, F., Payet, É., Vidal, G.: On the completeness of selective unification in concolic testing of logic programs. In: Hermenegildo, M.V., Lopez-Garcia, P. (eds.) LOPSTR 2016. LNCS, vol. 10184, pp. 205–221. Springer, Cham (2017). https://doi.org/10.1007/978-3-319-63139-4_12Mesnard, F., Payet, É., Vidal, G.: Selective unification in constraint logic programming. In: Vanhoof, W., Pientka, B. (eds.) PPDP, pp. 115–126. ACM (2017)Mesnard, F., Payet, É., Vidal, G.: Concolic Testing in CLP. CoRR abs/2008.00421 (2020). https://arxiv.org/abs/2008.00421Sen, K., Marinov, D., Agha, G.: CUTE: a concolic unit testing engine for C. In: ESEC/ FSE, pp. 263–272. ACM (2005)Ströder, T., Emmes, F., Schneider-Kamp, P., Giesl, J., Fuhs, C.: A linear operational semantics for termination and complexity analysis of ISO Prolog. In: Vidal, G. (ed.) LOPSTR 2011. LNCS, vol. 7225, pp. 237–252. Springer, Heidelberg (2012). https://doi.org/10.1007/978-3-642-32211-2_16Tikovsky, J.R.: Concolic testing of functional logic programs. In: Seipel, D., Hanus, M., Abreu, S. (eds.) WFLP/WLP/INAP -2017. LNCS (LNAI), vol. 10997, pp. 169–186. Springer, Cham (2018). https://doi.org/10.1007/978-3-030-00801-7_11Vidal, G.: Concolic execution and test case generation in prolog. In: Proietti, M., Seki, H. (eds.) LOPSTR 2014. LNCS, vol. 8981, pp. 167–181. Springer, Cham (2015). https://doi.org/10.1007/978-3-319-17822-6_10Wielemaker, J., Schrijvers, T., Triska, M., Lager, T.: SWI-prolog. TPLP 12(1–2), 67–96 (2012). https://doi.org/10.1017/S147106841100049

Some conceptual difficulties regarding "net" multipliers

Multipliers are routinely used for impact evaluation of private projects and public policies at the national and subnational levels. Oosterhaven and Stelder (2002) correctly pointed out the misuse of standard 'gross' multipliers and proposed the concept of 'net' multiplier as a solution to this bad practice. We prove their proposal is not well founded. We do so by showing that supporting theorems are faulty in enunciation and demonstration. The proofs are flawed due to an analytical error but the theorems themselves cannot be salvaged as generic, non-curiosum counterexamples demonstrate. We also provide a general analytical framework for multipliers and, using it, we show that standard 'gross' multipliers are all that is needed within the interindustry model since they follow the causal logic of the economic model, are well defined and independent of exogenous shocks, and are interpretable as predictors for change

A Termination Analyzer for Java Bytecode based on Path-Length

It is important to prove that supposedly terminating programs actuallyterminate, particularly if those programs must berun on critical systems or downloaded into a client such as a mobile phone.Although termination of computer programs is generally undecidable,it is possible and useful to provetermination of a large, non-trivial subset of the terminating programs.In this paper we present our termination analyser for sequential Java bytecode,based on a program property called path-length. We describe theanalyses which are needed before the path-length can be computed, such assharing, cyclicity and aliasing. Then weformally define the path-length analysis and prove it correct wrt areference denotational semantics of the bytecode. We show that a constraintlogic program P_CLPcan be built from the result of the path-length analysisof a Java bytecode program P andformally prove that if P_CLP terminates then also P terminates.Hence a termination prover for constraint logic programs can be appliedto prove the termination of P. We conclude with some discussion of thepossibilities and limitations of our approach.Ours is the first existing termination analyser for Java bytecodedealing with any kind of data structures dynamically allocated on the heapand which does not require any help or annotation on the part of the user

Revolving Doors: How Externalization Policies Block Refugees and Deflect Other Migrants across Migration Routes

Migrant destination states of the Global North generally seek to stem irregular migration while remaining committed to refugee rights. To do so, these states have increasingly sought to externalize migration control, implicating migrant origin and transit states in managing the movement of persons across borders. But do externalization policies actually have an impact on unauthorized migration flows? If yes, do those impacts vary across different migrant categories given that both asylum seekers and other migrants can cross borders without prior authorization? We argue that these policies do have an impact on unauthorized migration flows and that those impacts are distinct for refugees and other migrants. Using data on “irregular/illegal border crossings” collected by Frontex, the Border and Coast Guard Agency of the European Union (EU), we first find that the geographical trajectories of refugees and other migrants who cross EU borders without authorization are distinct. Using a novel method to estimate whether individuals are likely to obtain asylum in 31 European destination states, we find that “likely refugees” tend to be concentrated on a single, primary migratory route while “likely irregular migrants” may be dispersed across multiple routes. Through an event study analysis of the impact of the 2016 EU–Turkey Statement, a paradigmatic example of externalization, we show that the policy primarily blocked likely refugees while deflecting likely irregular migrants to alternative routes. Our findings ultimately highlight how externalization policies may fail to prevent unauthorized entries of irregular migrants while endangering refugee protection

Borders Start With Numbers: How Migration Data Create “Fake Illegals”

Sudden rises in migration across the borders of the Global North have persistently attracted substantial media attention and fueled hostility toward “irregular migrants” and “bogus refugees.” While existing qualitative studies have extensively criticized the migrant-refugee distinction, we offer unique quantitative evidence of how migration numbers and labels construct impressions of increased irregular migration while in fact creating “fake illegals.” We conduct a two-stage mixed-method analysis, demonstrating first that data on “irregular/illegal border crossings” (IBCs) published by Frontex have become an authoritative source of information on migration flows cited in a corpus of mainstream news media articles. We then posit that, while persecutions and violence in countries of origin may trigger migration, it is policies in destination states that determine who “is” and “isn’t” a refugee. In turn, we develop a novel method to divide IBCs into those who would likely obtain asylum in 31 European destination states (“likely refugees”) and those who would not (“likely irregular migrants”) across time given asylum acceptance rates by nationality. We estimate that between 2009 and 2021 most border crossers labeled as “irregular/illegal” (55.4%) were actually “likely refugees,” a proportion we estimate to be 75.5% at the peak of arrivals in 2015. Thus, we find that sudden and large increases in border crossings concentrated in space likely concern forced rather than irregular migrants. Altogether, our constructivist approach reveals how migration data and categories both influence and are influenced by securitized border policies and that, in this respect, borders start with numbers

Complexity of Bradley-Manna-Sipma Lexicographic Ranking Functions

In this paper we turn the spotlight on a class of lexicographic ranking functions introduced by Bradley, Manna and Sipma in a seminal CAV 2005 paper, and establish for the first time the complexity of some problems involving the inference of such functions for linear-constraint loops (without precondition). We show that finding such a function, if one exists, can be done in polynomial time in a way which is sound and complete when the variables range over the rationals (or reals). We show that when variables range over the integers, the problem is harder -- deciding the existence of a ranking function is coNP-complete. Next, we study the problem of minimizing the number of components in the ranking function (a.k.a. the dimension). This number is interesting in contexts like computing iteration bounds and loop parallelization. Surprisingly, and unlike the situation for some other classes of lexicographic ranking functions, we find that even deciding whether a two-component ranking function exists is harder than the unrestricted problem: NP-complete over the rationals and $\Sigma^P_2$-complete over the integers.Comment: Technical report for a corresponding CAV'15 pape

Active surveillance in renal transplant patients with prostate cancer: a multicentre analysis

Introduction: Due to medical improvements leading to increased life expectancy after renal transplantation and widened eligibility criteria allowing older patients to be transplanted, incidence of (low-risk) prostate cancer (PCa) is increasing among renal transplant recipients (RTR). It remains to be established whether active surveillance (AS) for PCa represents a safe treatment option in this setting. Therefore, we aim to compare AS discontinuation and oncological outcomes of AS for PCa of RTR vs. non-transplant patients. Methods: Multicentre study including RTR diagnosed with PCa between 2008 and 2018 in whom AS was initiated. A subgroup of non-RTR from the St. Antonius hospital AS cohort was used as a control group. Comparison of RTR vs. non-RTR was performed by 2:1 propensity score matched survival analysis. Outcome measures included tumour progression-free survival, treatment-free survival, metastasis rates, biochemical recurrence rates and overall survival. Patients were matched based on age, year of diagnosis, PSA, biopsy ISUP grade group, relative number of positive biopsy cores and clinical stage. Results: A total of 628 patients under AS were evaluated, including 17 RTRs and 611 non-RTRs. A total of 13 RTR cases were matched with 24 non-RTR cases. Median overall follow-up for the RTR and non-RTR matched cases was, respectively, 5.1 (IQR 3.2–8.7) years and 5.7 (IQR 4.8–8.1) years. There were no events of metastasis and biochemical recurrence among matched cases. The matched-pair analysis results in a 1-year and 5-year survival of the RTR and non-RTR patients were, respectively, 100 vs. 92%, and 39 vs. 76% for tumour progression, 100 vs. 91% and 59 vs. 76% for treatment-free survival and, respectively, 100 vs. 100% and 88 vs. 100% for overall survival. No significant differences in tumour progression-free survival (p = 0.07) and treatment-free survival were observed (p = 0.3). However, there was a significant difference in overall survival comparing both groups (p = 0.046). Conclusions: AS may be carefully considered in RTR with low-risk PCa. In our preliminary analysis, no major differences were present in AS outcomes between RTR and non-RTR. Overall mortality was significantly higher in the RTR subgroup

Migration outflows and optimal migration policy: rules versus discretion

We study the effects of more open borders on return migration and show that migrants are more likely to return to the origin country when migration rules are softened, because this implies that they could more easily re-migrate if return migration is unsuccessful. As a result, softening migration rules leads to lower net inflows than is generally acknowledged. We show that if government follows rules to shape the optimal migration policy, it will choose more open “borders” than were its behaviour to be discretionary. However, this requires an appropriate commitment technology. We show that electoral accountability may be a solution to the commitment problem. As a matter of fact, observed softer immigration rules in western countries suggest the effectiveness of such a mechanism.info:eu-repo/semantics/publishedVersio

Spontaneous focal activation of invariant natural killer T (iNKT) cells in mouse liver and kidney

<p>Abstract</p> <p>Background</p> <p>Invariant natural killer T (iNKT) cells differ from other T cells by their hyperactive effector T-cell status, in addition to the expression of NK lineage receptors and semi-invariant T-cell receptors. It is generally agreed that the immune phenotype of iNKT cells is maintained by repeated activation in peripheral tissues although no explicit evidence for such iNKT cell activity <it>in vivo </it>has so far been reported.</p> <p>Results</p> <p>We used an interferon (IFN)-γ-inducible cytoplasmic protein, Irga6, as a histological marker for local IFN-γ production. Irga6 was intensely expressed in small foci of liver parenchymal cells and kidney tubular epithelium. Focal Irga6 expression was unaffected by germ-free status or loss of TLR signalling and was totally dependent on IFN-γ secreted by T cells in the centres of expression foci. These were shown to be iNKT cells by diagnostic T cell receptor usage and their activity was lost in both CD1 d and Jα-deficient mice.</p> <p>Conclusions</p> <p>This is the first report that supplies direct evidence for explicit activation events of NKT cells <it>in vivo </it>and raises issues about the triggering mechanism and consequences for immune functions in liver and kidney.</p