No abstract

Abstract. The ability to perform strong updates is the main contributor to the precision of flow-sensitive pointer analysis algorithms. Traditional flow-sensitive pointer analyses cannot strongly update pointers residing in the heap. This is a severe restriction for Java programs. In this paper, we propose a new flow-sensitive pointer analysis algorithm for Java that can perform strong updates on heap-based pointers effectively. Instead of points-to graphs, we represent our points-to information as maps from access paths to sets of abstract objects. We have implemented our analysis and run it on several large Java benchmarks. The results show considerable improvement in precision over the points-to graph based flow-insensitive and flow-sensitive analyses, with reasonable running time.

Abstract. Memory models for shared-memory concurrent programming languages typically guarantee sequential consistency (SC) semantics for datarace-free (DRF) programs, while providing very weak or no guarantees for non-DRF programs. In effect programmers are expected to write only DRF programs, which are then executed with SC semantics. With this in mind, we propose a novel scalable solution for dataflow analysis of concurrent programs, which is proved to be sound for DRF programs with SC semantics. We use the synchronization structure of the program to propagate dataflow information among threads without requiring to consider all interleavings explicitly. Given a dataflow analysis that is sound for sequential programs and meets certain criteria, our technique automatically converts it to an analysis for concurrent programs.

Recently, an ultrahigh piezoelectricity (longitudinal piezoelectric coefficient d33 ~ 1500 pC/N) was reported in polycrystalline specimens of Sm-modified relaxor ferroelectric system Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) (Li et al 2018 Nat. Mater. 17 349). Here, we examine the factors associated with this anomalous phenomenon by carrying out a comparative structural, dielectric, ferroelectric and impedance spectroscopy on Sm-free 0.71PMN-0.29PT (piezoelectric coefficient d33 ~ 380 pC/N) and its Sm modified counterpart (d33 ~ 1160 pC/N). We found that, apart from inducing a Cm  →  P4mm inter-ferroelectric instability, Sm modification stabilizes a considerable degree of oxygen vacancies, with Sm exhibiting valence fluctuation. Based on our results, we argue that these defect types are the important source for creating structural-polar heterogeneity on the local scale, the interaction of which with the long-range ferroelectric order makes the system exhibit an ultrahigh piezoelectric response.

No abstract