Types Of Systems Research Articles

CoolerSpace: A Language for Physically Correct and Computationally Efficient Color Programming

Color programmers manipulate lights, materials, and the resulting colors from light-material interactions. Existing libraries for color programming provide only a thin layer of abstraction around matrix operations. Color programs are, thus, vulnerable to bugs arising from mathematically permissible but physically meaningless matrix computations. Correct implementations are difficult to write and optimize. We introduce CoolerSpace to facilitate physically correct and computationally efficient color programming. CoolerSpace raises the level of abstraction of color programming by allowing programmers to focus on describing the logic of color physics. Correctness and efficiency are handled by CoolerSpace. The type system in CoolerSpace assigns physical meaning and dimensions to user-defined objects. The typing rules permit only legal computations informed by color physics and perception. Along with type checking, CoolerSpace also generates performance-optimized programs using equality saturation. CoolerSpace is implemented as a Python library and compiles to ONNX, a common intermediate representation for tensor computations. CoolerSpace not only prevents common errors in color programming, but also does so without run-time overhead: even unoptimized CoolerSpace programs out-perform existing Python-based color programming systems by up to 5.7 times; our optimizations provide up to an additional 1.4 times speed-up.

Verified Lock-Free Session Channels with Linking

Type systems and program logics based on session types provide powerful high-level reasoning principles for message-passing concurrency. Modern versions employ bidirectional session channels that (1) are asynchronous so that send operations do not block, (2) have buffers in both directions so that both parties can send messages in parallel, and (3) feature a link operation (also called forward) to concisely write programs in process style. These features complicate a low-level lock-free implementation of channels and therefore increase the gap between the meta theory of prior work—which is verified w.r.t. a high-level semantics of channels (e.g., π-calculus)—and the code that runs on an actual computer. We address this problem by verifying a low-level lock-free implementation of session channels w.r.t. a high-level specification based on session types. We carry out our verification in a layered manner by employing the Iris framework for concurrent separation logic. We start with an abstract specification of (unidirectional) queues—of which we provide a linked-list and array-segment based implementation—and gradually build up to session channels with all of the aforementioned features. To make a layered verification possible we develop two logical abstractions—queues with ghost linking and pairing invariants—to reason about the atomicity and changing endpoints due to linking, respectively. All our results are mechanized in the Coq proof assistant.

A Typed Multi-level Datalog IR and Its Compiler Framework

The resurgence of Datalog in the last two decades has led to a multitude of new Datalog systems. These systems explore novel ideas for improving Datalog's programmability and performance, making important contributions to the field. Unfortunately, the individual systems progress at a much slower pace than the overall field, because improvements in one system are rarely ported to other systems. The reason for this rift is that each system provides its own Datalog dialect with specific notation, language features, and invariants, enabling specific optimization and execution strategies. This paper presents the first compiler framework for Datalog that can be used to support any Datalog frontend language and to target any Datalog backend. The centerpiece of our framework is a novel typed multi-level Datalog IR that supports IR extensions and guarantees executability. Existing Datalog systems can provide a compiler frontend that translates their Datalog dialect to the extended IR. The IR is then progressively lowered toward core Datalog, allowing optimizations at each level. At last, compiler backends can target different Datalog solvers. We have implemented the compiler framework and integrated 4 Datalog frontends and 3 Datalog backends, using 16 IR extensions. We also formalize the IR's flexible type system, which is bidirectional, flow-sensitive, bipolar, and uses three-valued typing contexts. The type system simultaneously validates type compatibility and precisely tracks bindings of logic variables while permitting IR extensions.

Law and Order for Typestate with Borrowing

Typestate systems are notoriously complex as they require sophisticated machinery for tracking aliasing. We propose a new, transition-oriented foundation for typestate in the setting of impure functional programming. Our approach relies on ordered types for simple alias tracking and its formalization draws on work on bunched implications. Yet, we support a flexible notion of borrowing in the presence of typestate. Our core calculus comes with a notion of resource types indexed by an ordered partial monoid that models abstract state transitions. We prove syntactic type soundness with respect to a resource-instrumented semantics. We give an algorithmic version of our type system and prove its soundness. Algorithmic typing facilitates a simple surface language that does not expose tedious details of ordered types. We implemented a typechecker for the surface language along with an interpreter for the core language.

Imperative Compositional Programming: Type Sound Distributive Intersection Subtyping with References via Bidirectional Typing

Compositional programming is a programming paradigm that emphasizes modularity and is implemented in the CP programming language. The foundations for compositional programming are based on a purely functional variant of System F with intersection types, called Fi+, which includes distributivity rules for subtyping. This paper shows how to extend compositional programming and CP with mutable references, enabling a modular, imperative compositional programming style. A technical obstacle solved in our work is the interaction between distributive intersection subtyping and mutable references. Davies and Pfenning [2000] studied this problem in standard formulations of intersection type systems and argued that, when combined with references, distributive subtyping rules lead to type unsoundness. To recover type soundness, they proposed dropping distributivity rules in subtyping. CP cannot adopt this solution, since it fundamentally relies on distributivity for modularity. Therefore, we revisit the problem and show that, by adopting bidirectional typing, a more lightweight and type sound restriction is possible: we can simply restrict the typing rule for references. This solution retains distributivity and an unrestricted intersection introduction rule. We present a first calculus, based on Davies and Pfenning's work, which illustrates the generality of our solution. Then we present an extension of Fi+ with references, which adopts our restriction and enables imperative compositional programming. We implement an extension of CP with references and show how to model a modular live-variable analysis in CP. Both calculi and their proofs are formalized in the Coq proof assistant.

Multris: Functional Verification of Multiparty Message Passing in Separation Logic

We introduce Multris, a separation logic for verifying functional correctness of programs that combine multiparty message-passing communication with shared-memory concurrency. The foundation of our work is a novel concept of multiparty protocol consistency, which guarantees safe communication among a set of parties, provided each party adheres to its prescribed protocol. Our concept of protocol consistency is inspired by the bottom-up approach for multiparty session types. However, by considering it in the context of separation logic instead of a type system, we go further in terms of generality by supporting new notions of implicit transfer of knowledge and implicit transfer of resources. We develop tactics for automatically verifying protocol consistency and for reasoning about message-passing operations in Multris. We evaluate Multris on a range of examples, including the well-known two- and three-buyer protocols, as well as a new verification benchmark based on Chang and Roberts's ring leader election protocol. To ensure the reliability of our work, we prove soundness of Multris w.r.t. a low-level channel semantics using the Iris framework in Coq.

Realistic Realizability: Specifying ABIs You Can Count On

The Application Binary Interface (ABI) for a language defines the interoperability rules for its target platforms, including data layout and calling conventions, such that compliance with the rules ensures “safe” execution and perhaps certain resource usage guarantees. These rules are relied upon by compilers, libraries, and foreign-function interfaces. Unfortunately, ABIs are typically specified in prose, and while type systems for source languages have evolved, ABIs have comparatively stalled, lacking advancements in expressivity and safety. We propose a vision for richer, semantic ABIs to improve interoperability and library integration, supported by a methodology for formally specifying ABIs using realizability models. These semantic ABIs connect abstract, high-level types to unwieldy, but well-behaved, low-level code. We illustrate our approach with a case study formalizing the ABI of a functional source language in terms of a reference-counting implementation in a C-like target language. A key contribution supporting this case study is a graph-based model of separation logic that captures the ownership and accessibility of reference-counted resources using modalities inspired by hybrid logic. To highlight the flexibility of our methodology, we show how various design decisions can be interpreted into the semantic ABI. Finally, we provide the first formalization of library evolution, a distinguishing feature of Swift’s ABI.

Semantic-Type-Guided Bug Finding

In recent years, there has been an increased interest in tools that establish incorrectness rather than correctness of program properties. In this work we build on this approach by developing a novel methodology to prove incorrectness of semantic typing properties of functional programs, extending the incorrectness approach to the model theory of functional program typing. We define a semantic type refuter which refutes semantic typings for a simple functional language. We prove our refuter is co-recursively enumerable, and that it is sound and complete with respect to a semantic typing notion. An initial implementation is described which uses symbolic evaluation to efficiently find type errors over a functional language with a rich type system.

Crabtree: Rust API Test Synthesis Guided by Coverage and Type

Rust type system constrains pointer operations, preventing bugs such as use-after-free. However, these constraints may be too strict for programming tasks such as implementing cyclic data structures. For such tasks, programmers can temporarily suspend checks using the unsafe keyword. Rust libraries wrap unsafe code blocks and expose higher-level APIs. They need to be extensively tested to uncover memory-safety bugs that can only be triggered by unexpected API call sequences or inputs. While prior works have attempted to automatically test Rust library APIs, they fail to test APIs with common Rust features, such as polymorphism, traits, and higher-order functions, or they have scalability issues and can only generate tests for a small number of combined APIs. We propose Crabtree, a testing tool for Rust library APIs that can automatically synthesize test cases with native support for Rust traits and higher-order functions. Our tool improves upon the test synthesis algorithms of prior works by combining synthesis and fuzzing through a coverage- and type-guided search algorithm that intelligently grows test programs and input corpus towards testing more code. To the best of our knowledge, our tool is the first to generate well-typed tests for libraries that make use of higher-order trait functions. Evaluation of Crabtree on 30 libraries found four previously unreported memory-safety bugs, all of which were accepted by the respective authors.

Gradient: Gradual Compartmentalization via Object Capabilities Tracked in Types

Modern software needs fine-grained compartmentalization, i.e., intra-process isolation. A particularly important reason for it are supply-chain attacks, the need for which is aggravated by modern applications depending on hundreds or even thousands of libraries. Object capabilities are a particularly salient approach to compartmentalization, but they require the entire program to assume a lack of ambient authority. Most of existing code was written under no such assumption; effectively, existing applications need to undergo a rewrite-the-world migration to reap the advantages of ocap. We propose gradual compartmentalization , an approach which allows gradually migrating an application to object capabilities, component by component in arbitrary order, all the while continuously enjoying security guarantees. The approach relies on runtime authority enforcement and tracking the authority of objects the type system. We present Gradient, a proof-of-concept gradual compartmentalization extension to Scala which uses Enclosures and Capture Tracking as its key components. We evaluate our proposal by migrating the standard XML library of Scala to Gradient.

Programmable MCMC with Soundly Composed Guide Programs

Probabilistic programming languages (PPLs) provide language support for expressing flexible probabilistic models and solving Bayesian inference problems. PPLs with programmable inference make it possible for users to obtain improved results by customizing inference engines using guide programs that are tailored to a corresponding model program. However, errors in guide programs can compromise the statistical soundness of the inference. This article introduces a novel coroutine-based framework for verifying the correctness of user-written guide programs for a broad class of Markov chain Monte Carlo (MCMC) inference algorithms. Our approach rests on a novel type system for describing communication protocols between a model program and a sequence of guides that each update only a subset of random variables. We prove that, by translating guide types to context-free processes with finite norms, it is possible to check structural type equality between models and guides in polynomial time. This connection gives rise to an efficient type-inference algorithm for probabilistic programs with flexible constructs such as general recursion and branching. We also contribute a coverage-checking algorithm that verifies the support of sequentially composed guide programs agrees with that of the model program, which is a key soundness condition for MCMC inference with multiple guides. Evaluations on diverse benchmarks show that our type-inference and coverage-checking algorithms efficiently infer types and detect sound and unsound guides for programs that existing static analyses cannot handle.

Refinement Type Refutations

Refinement types combine SMT decidable constraints with a compositional, syntax-directed type system to provide a convenient way to statically and automatically check properties of programs. However, when type checking fails, programmers must use cryptic error messages that, at best, point out the code location where a subtyping constraint failed to determine the root cause of the failure. In this paper, we introduce refinement type refutations, a new approach to explaining why refinement type checking fails, which mirrors the compositional way in which refinement type checking is carried out. First, we show how to systematically transform standard bidirectional type checking rules to obtain refutations. Second, we extend the approach to account for global constraint-based refinement inference via the notion of a must-instantiation: a set of concrete inhabitants of the types of subterms that suffice to demonstrate why typing fails. Third, we implement our method in HayStack—an extension to LiqidHaskell which automatically finds type-refutations when refinement type checking fails, and helps users understand refutations via an interactive user-interface. Finally, we present an empirical evaluation of HayStack using the regression benchmark-set of LiqidHaskell, and the benchmark set of G2, a previous method that searches for (non-compositional) counterexample traces by symbolically executing Haskell source. We show that HayStack can find refutations for 99.7% of benchmarks, including those with complex typing constructs (e.g., abstract and bounded refinements, and reflection), and does so, an order of magnitude faster than G2.

Development of an INDEL typing system for <i>ctx</i>+ strains of <i>Vibrio cholerae</i> from the seventh pandemic

BACKGROUND: The seventh cholera pandemic is accompanied by the formation of Vibrio cholerae clones with new genetic properties, including those with the ability to spread pandemically and cause diseases with a more severe clinical course. The widespread distribution of such genetic variants of Vibrio cholerae and the possibility of their introduction into the territory of the Russian Federation necessitate constant comprehensive monitoring using modern molecular genetic technologies. AIM: To improve INDEL typing of ctx+ strains of V. cholerae of the seventh pandemic by using additional INDEL loci. Materials and methods: A bioinformatic analysis of 2105 full-genome sequences of toxigenic ctxAB+tcpA+ strains of Vibrio cholerae O1 El Tor from open databases was carried out in order to search for INDEL loci for molecular typing. Based on the convenience criterion for allele size identification, eight INDEL loci were selected. Three loci have been described previously, and five were identified as a result of this work. The designed primers formed amplicons ranging in size from 67 to 390 base pairs, which made it possible to confidently identify them during gel electrophoresis. Results: The distribution of alleles formed 11 unique INDEL clusters, which we designated A-K. Based on the number of strains within the clusters, three types of clusters were identified: major (A, B and C) made up 89% of the total number of sequences studied, intermediate (D, E, F, G and H) 10.5% of the genomes. Three minor clusters (I, J and K) were represented by single strains. Four clusters united strains isolated in the 20th century (A — in 1941, F — in 1957, G — in 1993, E — in 1999), and seven clusters — in the 21st century in the period from 2003 to 2016. In the period from 2019 to 2023, representatives of INDEL clusters were active: A, B, D and E. ConclusionS: The study of the timing of circulation suggested that representatives of different clusters have different epidemic potential, which was manifested in the absence of isolation of strains of some clusters in recent years. A comparative study of INDEL typing with SNP typing in the in silico analysis of 378 genomes of strains isolated on the African continent indicates that the proposed INDEL typing method is not inferior to SNP typing in terms of resolution.

A case of isolated dystextia due to subcortical infarction: a novel condition of digital device era

BackgroundIn recent years, cases of dystextia (texting disabilities) and dystypia (typing disabilities) have been reported. However, reports describing isolated dystextia without aphasia or other cognitive impairments are rare, and the detailed pathophysiology is not fully understood. Most Japanese people use the alphabetical spelling system (Romaji) for texting and typing. Herein, we report the case of a man with isolated dystextia and dystypia resulting from Romaji conversion difficulties.Case presentationA 48-year-old, right-handed Japanese man developed texting and typing difficulties. The standard neuropsychological tests showed no signs of aphasia or other cognitive impairments, except for slight executive dysfunction. Thus, isolated dystextia and dystypia were diagnosed. Furthermore, the patient experienced Romaji conversion difficulties. Magnetic resonance imaging revealed a subcortical infarction in the left cerebral hemisphere. Single photon emission tomography revealed hypoperfusion, including in the left dorsolateral frontal cortex.ConclusionsThe left dorsolateral frontal cortex may be related to Romaji conversion in Japanese individuals. Therefore, diaschisis of the left dorsolateral frontal cortex due to subcortical lesions may have impaired Romaji conversion, leading to dystextia and dystypia, in this patient.

Performance and PV benefits analysis of multi-source renewable energy systems for different types of buildings on university campus

Due to the large campus area and high personnel density, universities experience significant building energy consumption. The comprehensive utilization of renewable energy can greatly alleviate energy consumption in higher education institutions. To explore the application prospects of renewable energy systems in universities, this study takes a university in Wuhan as a case example, investigating the performance and potential of various types of Photovoltaic-assisted Heating, Ventilation, and Air Conditioning (PV-HVAC) systems. First, the building load was calculated using DeST software. Subsequently, the potential for solar energy application on campus was assessed using a combination of QGIS, Labelme, and Python. Moreover, three types of PV-HVAC systems were designed for five categories of buildings based on their distinct characteristics, and TRNSYS software was utilized for performance simulation and analysis. The results indicate that the annual performance coefficients of the three systems are 3.8, 3.2, and 4.5, with corresponding annual energy self-sufficiency rates of 114 %, 72 %, and 32 %, respectively. Finally, the overall energy self-sufficiency rate of the PV-HVAC system across the campus is 65 %. This research provides valuable insights for achieving nearly zero-energy HVAC systems in university campuses.

6971 Effects of the Hybrid Closed-loop System in Pediatric-Onset Type 1 Diabetes

Abstract Disclosure: H. Woo: None. J. Yoo: None. S. Shin: None. Y. Lee: None. H. Kim: None. M. Gu: None. J. Kim: None. J. Kim: None. C. Shin: None. Y. Lee: None. Purpose: We evaluated the effectiveness and limitations of the MiniMedTM 770G, a hybrid closed-loop (HCL) system which adjusts basal insulin every five minutes using continuous glucose monitoring (CGM) data, for glycemic control in pediatric-onset type 1 diabetes (T1D) in South Korea. Methods: We enrolled 20 patients (10 boys and 10 girls) who had been using the 770G pump for over three months, initiating its use between February 2022 and May 2023. Prior to this, they were CGM users and were followed for over a year post T1D diagnosis. Clinical and biochemical data, along with CGM metrics such as time in range (TIR), time below range (TBR), time above range (TAR), and coefficient of variation (CV), were analyzed. Additionally, the percentage of SmartGuard Auto Mode system usage was collected. Results: The median age at the start of 770G was 13.97 years (IQR 11.24–17.86), with a median of 6.5 years of duration of type 1 diabetes. After utilizing the 770G pump (n=20), TIR, TAR, and CV improved over the year (P<0.05). Patients utilizing Auto Mode over 85% of the time exhibited significant improvements in HbA1c (P=0.02), TIR (P=0.04), CV (P<0.01), and TAR 250 (P=0.02), in contrast to those who used Auto Mode 85% or less. Hyperglycemia and lack of calibration contributed to over 50% of the exits from Auto Mode. Conclusions: The implementation of HCL in adolescents and young adults with T1D enhanced glycemic control over one year. Educating patients on sustained Auto Mode use without interruptions is crucial. Presentation: 6/2/2024

Cross-comparison of the optical and acoustical calibration methods for microphones based on microelectromechanical system technologies

Calibration methods and associated international standards in airborne acoustics have enabled national metrology institutes to establish and maintain a fully defined traceability chain for designated laboratories and end users of microphones. However, such microphones need to be reciprocal, of condenser type and of specific dimensions; this, in effect, does not allow for the calibration of alternative existing sensor technologies and creates a further obstacle for the calibration of emerging technologies. An example relates to microphones based on microelectromechanical systems which are an integral part of a wide range of electronic devices; yet, there is no established calibration traceability chain other than methods employed by manufacturers. From a metrological perspective, new calibration methods that can accommodate microphones regardless of their size, reciprocal nature and utilised technology must be developed and subsequently standardised and adopted. This paper discusses the optical calibration method based on free field photon correlation and the acoustical calibration methods based on pressure comparison and free field substitution. These approaches can provide traceability to the international measurement standard system for novel types of microphones, and the measurement results showed themselves to be consistent. Based on this study, the possibility of expanding the new standard system was investigated.

Blow-up criteria for a two-component Camassa–Holm type system with cubic nonlinearity

Blow-up criteria for a two-component Camassa–Holm type system with cubic nonlinearity

Revisiting typing systems for group B Streptococcus prophages: an application in prophage detection and classification in group B Streptococcus isolates from Argentina.

Group B Streptococcus (GBS) causes severe infections in neonates and adults with comorbidities. Prophages have been reported to contribute to GBS evolution and pathogenicity. However, no studies are available to date on the presence and diversity of prophages in GBS isolates from humans in South America. This study provides insights into the prophage content of 365 GBS isolates collected from clinical samples in the context of an Argentinean multicentric study. Using whole-genome sequence data, we implemented two previously proposed methods for prophage typing: a PCR approach (carried out in silico) coupled with a blastx-based method to classify prophages based on their prophage group and integrase type, respectively. We manually searched the genomes and identified 325 prophages. However, only 80% of prophages could be accurately categorized with the previous approaches. Integration of phylogenetic analysis, prophage group and integrase type allowed for all to be classified into 19 prophage types, which correlated with GBS clonal complex grouping. The revised prophage typing approach was additionally improved by using a blastn search after enriching the database with ten new genes for prophage group classification combined with the existing integrase typing method. This modified and integrated typing system was applied to the analysis of 615 GBS genomes (365 GBS from Argentina and 250 from public databases), which revealed 29 prophage types, including two novel integrase subtypes. Their characterization and comparative analysis revealed major differences in the lysogeny and replication modules. Genes related to bacterial fitness, virulence or adaptation to stressful environments were detected in all prophage types. Considering prophage prevalence, distribution and their association with bacterial virulence, it is important to study their role in GBS epidemiology. In this context, we propose the use of an improved and integrated prophage typing system suitable for rapid phage detection and classification with little computational processing.

Real Time Prediction and Modelling of Power Grid System Stability and Load Balancing

Abstract The extensive geographical distribution of the power system determines its highly complex structure. The system includes key components such as generators, substations, transmission and distribution grids, and users. This system has characteristics such as nonlinearity, time-varying, and parameter uncertainty. Power system stability is inherently linked to its regular operational performance. This article uses Simulink models to simulate the working state of generators and circuit breakers during faults. Under the conditions of a synchronous generator with a rated power of 350MW, a voltage of 10.5KV, a three-phase parallel RLC load rated voltage of 115KV, and a power consumption of 300MW, when a short occurs on line, the speed and relative angle of the generator tend to a fixed value, and the system remains stable. When a fault occurs in the circuit within 0.1 seconds, the circuit breaker will cut off the faulty line within 0.6 seconds. Avoiding the occurrence of oscillations and unstable states in typical dynamic systems.