Program representation size in an intermediate language with intersection and union types

The CIL compiler for core Standard ML compiles whole programs using a novel typed intermediate language (TIL) with intersection and union types and flow labels on both terms and types. The CIL term representation duplicates portions of the program where intersection types are introduced and union types are eliminated. This duplication makes it easier to represent type information and to introduce customized data representations. However, duplication incurs compile-time space costs that are potentially much greater than are incurred in TILs employing type-level abstraction or quantification. In this paper, we present empirical data on the compile-time space costs of using CIL as an intermediate language. The data shows that these costs can be made tractable by using sufficiently fine-grained flow analyses together with standard hash-consing techniques. The data also suggests that non-duplicating formulations of intersection (and union) types would not achieve significantly better space complexity.National Science Foundation (CCR-9417382, CISE/CCR ESS 9806747); Sun grant (EDUD-7826-990410-US); Faculty Fellowship of the Carroll School of Management, Boston College; U.K. Engineering and Physical Sciences Research Council (GR/L 36963, GR/L 15685

On the basis for ELF - An Extensible Language Facility

Computer language for data processing and information retrieva

Kinesin's backsteps under mechanical load

Kinesins move processively toward the plus end of microtubules by hydrolyzing ATP for each step. From an enzymatic perspective, the mechanism of mechanical motion coupled to the nucleotide chemistry is often well explained using a single-loop cyclic reaction. However, several difficulties arise in interpreting kinesin's backstepping within this framework, especially when external forces oppose the motion of kinesin. We review evidence, such as an ATP-independent stall force and a slower cycle time for backsteps, that has emerged to challenge the idea that kinesin backstepping is due to ATP synthesis, i.e., the reverse cycle of kinesin's forward-stepping chemomechanics. Supplementing the conventional single-loop chemomechanics with routes for ATP-hydrolyzing backward steps and nucleotide-free steps, especially under load, gives a better physical interpretation of the experimental data on backsteps.Comment: 5 figures and 2 table

Transnational Judicial Dialogue and Evolving Jurisprudence in the Process of European Legal Integration

European legal integration can be envisioned as containing two dimensions of legal integration: vertical and horizontal. Vertical legal integration is a top down process where the establishment of a hierarchical legal order of courts and laws causes national courts to make more similar decisions over time as they increasingly come under the formal authority of a higher court. The European legal integration literature speaks mainly to vertical, formal, legal integration where the ECJ and EU law have asserted themselves as a formal authority over the national courts of the member states and compel the integration of the national courts. Horizontal legal integration involves national courts making more similar decisions over time because the national courts interact, borrow, and imitate each other informally. Vertical legal integration can compel national courts to take into account EU law and ECJ precedent, but it cannot control for variances in interpretation. The focus of this paper is not just on how the power dynamics of courts and laws have changed in Europe, but also how the legal realm of Europe has shifted to a greater frequency of shared legal outcomes. There have been hints in the European integration literature about horizontal legal integration in many vertical integration studies (See Jupille and Caporaso 2009; Burley and Mattli 1993; Mattli and Slaughter 1995). This paper will pursue further the notion that there are distinct dynamics of horizontal and informal legal integration and that horizontal legal integration in conjunction with vertical legal integration can contribute to a more complete understanding of the process of European legal integration. In this paper I argue that the historical progression of increasingly autonomous and powerful national courts (court empowerment) in Western Europe has allowed a process of transnational judicial dialogue to occur. Transnational judicial dialogue is composed of horizontal, transnational interactions between national high courts judges, where judges across countries voluntarily draw upon each other‟s rulings, logics, and academic writings and incorporate them into their own logics and rulings. I argue that this process of transnational judicial dialogue has furthered legal integration through the transmission of jurisprudence and legal concepts between different member state national judiciaries through informal, horizontal legal integration

Collapsing towers of interpreters

Given a tower of interpreters, i.e., a sequence of multiple interpreters interpreting one another as input programs, we aim to collapse this tower into a compiler that removes all interpretive overhead and runs in a single pass. In the real world, a use case might be Python code executed by an x86 runtime, on a CPU emulated in a JavaScript VM, running on an ARM CPU. Collapsing such a tower can not only exponentially improve runtime performance, but also enable the use of base-language tools for interpreted programs, e.g., for analysis and verification. In this paper, we lay the foundations in an idealized but realistic setting. We present a multi-level lambda calculus that features staging constructs and stage polymorphism: based on runtime parameters, an evaluator either executes source code (thereby acting as an interpreter) or generates code (thereby acting as a compiler). We identify stage polymorphism, a programming model from the domain of high-performance program generators, as the key mechanism to make such interpreters compose in a collapsible way. We present Pink, a meta-circular Lisp-like evaluator on top of this calculus, and demonstrate that we can collapse arbitrarily many levels of self-interpretation, including levels with semantic modifications. We discuss several examples: compiling regular expressions through an interpreter to base code, building program transformers from modi ed interpreters, and others. We develop these ideas further to include reflection and reification, culminating in Purple, a reflective language inspired by Brown, Blond, and Black, which realizes a conceptually infinite tower, where every aspect of the semantics can change dynamically. Addressing an open challenge, we show how user programs can be compiled and recompiled under user-modified semantics.Parts of this research were supported by ERC grant 321217, NSF awards 1553471 and 1564207, and DOE award DE-SC0018050

Automated Instruction Stream Throughput Prediction for Intel and AMD Microarchitectures

An accurate prediction of scheduling and execution of instruction streams is a necessary prerequisite for predicting the in-core performance behavior of throughput-bound loop kernels on out-of-order processor architectures. Such predictions are an indispensable component of analytical performance models, such as the Roofline and the Execution-Cache-Memory (ECM) model, and allow a deep understanding of the performance-relevant interactions between hardware architecture and loop code. We present the Open Source Architecture Code Analyzer (OSACA), a static analysis tool for predicting the execution time of sequential loops comprising x86 instructions under the assumption of an infinite first-level cache and perfect out-of-order scheduling. We show the process of building a machine model from available documentation and semi-automatic benchmarking, and carry it out for the latest Intel Skylake and AMD Zen micro-architectures. To validate the constructed models, we apply them to several assembly kernels and compare runtime predictions with actual measurements. Finally we give an outlook on how the method may be generalized to new architectures.Comment: 11 pages, 4 figures, 7 table

Interpreters and the Writing of History in China

This article argues that interpreters are crucial figures in the recording of history. Evidence taken from historical texts in ancient China is used to verify the claim that interpreters’ notes might have been used as a reference in composing historical records. By documenting the Tang dynasty (AD 618-907) policy to have interpreters interview foreign envoys and submit the relevant accounts to the Bureau of Historiography, this article provides background for the link between interpreters’ interview notes and history compilation in China. Evidence is further drawn from the history of the Sui dynasty (AD 581-618), whereby an interpreter’s mediated account of the emperor’s conversation with a Japanese envoy was directly adapted. Most interestingly, pictorial and written documents of foreign peoples made in the mid-6th century during the Liang dynasty (AD 502-557) were found to be very similar to the written accounts about these foreign peoples in Liangshu, the history of the Liang dynasty, completed in the early 7th century. Apparently, there is a solid link between the interview accounts and historical accounts about foreign peoples in China. Thus, there is a strong possibility that interpreters’ notes, in the form of reports, provide important, if not primary, sources for history compilation in China.Le présent article soutient l’idée que les interprètes sont des personnages importants dans la consignation des évènements historiques. Des données puisées dans les textes historiques de la Chine ancienne ont été utilisées pour vérifier l’hypothèse selon laquelle des notes des interprètes auraient été consultées pendant la constitution des dossiers historiques. En montrant que la politique de la dynastie des Tang (618-907 ap. J.-C.) consistait à demander aux interprètes de mener des entretiens avec les envoyés étrangers et de remettre les comptes rendus au Bureau de l’historiographie, l’article fournit un cadre permettant de faire le lien entre les notes d’entretien des interprètes et la consignation historique en Chine. D’autres données ont été relevées à partir de l’histoire de la dynastie des Sui (581-618 ap. J.-C.), selon laquelle un compte rendu de la conversation entre l’empereur et un envoyé japonais, effectué par un interprète, a été directement adapté. Plus intéressants encore, les documents écrits et figurés sur des peuples étrangers produits vers la moitié du vie siècle, pendant la dynastie des Liang (502-557 ap. J.-C.), ressemblaient beaucoup aux comptes rendus du Liangshu, c’est-à-dire l’histoire de la dynastie des Liang qui a été terminée au début du viie siècle. Il existerait donc un rapport étroit entre les comptes rendus d’entretiens et les comptes rendus historiques sur les peuples étrangers en Chine. Par conséquent, il est fortement probable que les notes des interprètes, sous la forme de rapports, constituaient des sources importantes, sinon primordiales, pour la consignation des évènements historiques en Chine