Imperative Programming Research Articles

Precise quantitative information flow analysis— a symbolic approach

Quantitative information flow analysis (QIF) is a portfolio of software security assessment techniques measuring the amount of confidential information leaked by a program to its public outputs. In this paper, we extend the scope of precise QIF for deterministic imperative programs where information flow can be described with linear integer arithmetic. We propose two novel QIF analyses that precisely measure both residual Shannon entropy and min-entropy of the secret and that feature improved tolerance to large leaks and large input domains.For this purpose, we investigate the use of program specifications in QIF. We present criteria for specification admissibility and a program analysis that replaces exhaustive program exploration with symbolic execution, while incorporating user-supplied (but machine-checked) specifications. This kind of program analysis allows to trade automation for scalability, e.g., to programs with unbounded loops. Furthermore, we show how symbolic projection and counting, based in this instance on symbolic manipulation of polyhedra, avoid subsequent leak enumeration and enable precise QIF for programs with large leaks.

Programación genérica en C++, usando Metaprogramación

La complejidad de nuestros programas, va en aumento con los problemas a los que nos enfrentamos. Una forma de darle solución, es repetir una y otra vez las mismas estructuras, tal como nos acostumbró la programación tradicional o imperativa. este artículo, explora las relaciones entre plantillas C++, la programación genérica y la habilidad de desarrollar computaciones estáticas y generación de código. Muchos desarrolladores aplicaciones en computación científica; y el mecanismo de las plantillas en C++ les permite resolver importantes problemas en el diseño de librerías de clase.

Inference of polynomial invariants for imperative programs: A farewell to Gröbner bases

The article presents a static analysis for computing polynomial invariants for imperative programs. The analysis is derived from an abstract interpretation of a backwards semantics, and computes preconditions for equalities of the form g=0 to hold at the end of execution. A distinguishing feature of the technique is that it computes polynomial loop invariants without resorting to Gröbner base computations. The analysis uses remainder computations over parameterized polynomials in order to handle conditionals and loops efficiently. The algorithm can analyze and find a large majority of loop invariants reported previously in the literature, and executes significantly faster than implementations using Gröbner bases.

A new software for fragment-based QSAR and its applications

Fragment-based methods are quite popular in 2D QSAR/QSPR studies. In the advanced versions of these approaches for developing highly predictive models, one have to generate a huge set of descriptors that in turn requires well-designed algorithms and high-quality parallelism. To overcome these problems we developed the software for tagged generation of fragmental descriptors. One of the most perspective programming paradigms is functional programming. Programs in pure functional languages are easy to parallelize, tend to be faultless, more clear, easy extensible [1]. Despite its tangible complexity for learning, functional programming is becoming rather popular, recently several chemoinformatics frameworks: OUCH and chemf were presented. We developed the program QLab for the fragmentation of molecular graphs in the imperative programming language (Java, using CDK), and ported it under the name FragmenT into the functional language (Haskell). Aware of the fact that graph operations is a core of chemoinformatics, FragmenT represents chemical structures by means of Functional Graph Library – a powerful tool for graph operations [2]. Using this software we processed several structure-activity/property databases containing hundreds of compounds and generated the sets of more than 500 000 fragmental descriptors in each case. Then for each database 100 most correlated with activity/property descriptors were selected using stagewise MLR. Based on selected descriptors the predictive models were developed using artificial neural networks (ANN) and Random Forest algorithms. Comparison with other fragmental descriptors generation software showed better predictive ability of our models.

모나드를 이용한 비결정적 컴파일러 구현

본 연구에서는 Haskell의 모나드 기법을 이용한 명령형 언어의 컴파일러 구현에 대해 논의한다. 이 컴파일러는 한 생성 룰이 입력 스트링의 파싱을 실패할 때 다른 생성 룰로써 파싱하는 backtracking 기능의 비 결정적 Recursive Descent Parser를 포함한다. Haskell은 파싱에 필요한 우수한 기능들을 가지고 있다. Haskell의 대수적 타입은 추상구문트리를 자연스럽게 표현할 수 있으며, 모나드 파싱을 적용한 프로그램 코드는 매우 간결하여 가독성이 좋고, 타 언어에 의해 구현된 것에 비해 코드의 양이 획기적으로 감소된다. 이 컴파일러의 목적 코드는 스택 머신을 기반으로 한 Stack-Assembly 언어로서 이것을 위한 코드 생성과 어셈블러 실행 환경에 대해서도 논의한다. We discuss the implementation of a compiler for an imperative programming language, using monad in Haskell. This compiler involves a recursive-descent parser conducting nondeterministic parsing, in which backtracking occurs to try with other rules when the application of a production rule fails to parse an input string. Haskell has some strong facilities for parsing. Its algebraic types represent abstract syntax trees in a smooth way, and program codes by monad parsing are so concise that they are highly readable and code size is reduced significantly, comparing with other languages. We also deal with the runtime environment of the assembler and code generation whose target is the Stack-Assembly language based on a stack machine.

Parallel gesture recognition with soft real-time guarantees

Using imperative programming to process event streams, such as those generated by multi-touch devices and 3D cameras, has significant engineering drawbacks. Declarative approaches solve common problems but so far, they have not been able to scale on multicore systems while providing guaranteed response times.We propose PARTE, a parallel scalable complex event processing engine that allows for a declarative definition of event patterns and provides soft real-time guarantees for their recognition. The proposed approach extends the classical Rete algorithm and maps event matching onto a graph of actor nodes. Using a tiered event matching model, PARTE provides upper bounds on the detection latency by relying on a combination of non-blocking message passing between Rete nodes and safe memory management techniques.The performance evaluation shows the scalability of our approach on up to 64 cores. Moreover, it indicates that PARTE's design choices lead to more predictable performance compared to a PARTE variant without soft real-time guarantees. Finally, the evaluation indicates further that gesture recognition can benefit from the exposed parallelism with superlinear speedups.

Universal Style Sheet Language Environment Modification for the Business Use

This paper deals with the description of USSL – Universal Style Sheet Language environment. USSL style sheet language is platform-independent and its primary focus is the declarative notation of the appearance of GUI libraries used by imperative programming languages. The implementation of the software support for wxWidgets library is made, because this library has no support for the separate declarative notation of the appearance via style sheet language. The separation of the appearance enables us to reuse and standardize the appearance notation and the independent development of the appearance. In this way it is possible to achieve consistent appearance of applications of specific set or even all of company software products. However, the first proposal of the USSL has several disadvantages which restrict the possibilities for practical use in business or other environment. These disadvantages are: the lack of @import rule for importing other style sheets, USSL only supports basic set of selectors compared with selectors of other style sheet languages for desktop environment such as Qt QSS and GTK+ GtkCssProvider, the lack of styling of the cursors, it is impossible to put down URL. The placement of widgets and its borders are not solved either. This paper contains suggestions for solving these issues.

Modular reasoning about concurrent higher-order imperative programs

Modular reasoning about concurrent higher-order imperative programs

Frequent statement and dereference elimination for imperative and object-oriented distributed programs.

This paper introduces new approaches for the analysis of frequent statement and dereference elimination for imperative and object-oriented distributed programs running on parallel machines equipped with hierarchical memories. The paper uses languages whose address spaces are globally partitioned. Distributed programs allow defining data layout and threads writing to and reading from other thread memories. Three type systems (for imperative distributed programs) are the tools of the proposed techniques. The first type system defines for every program point a set of calculated (ready) statements and memory accesses. The second type system uses an enriched version of types of the first type system and determines which of the ready statements and memory accesses are used later in the program. The third type system uses the information gather so far to eliminate unnecessary statement computations and memory accesses (the analysis of frequent statement and dereference elimination). Extensions to these type systems are also presented to cover object-oriented distributed programs. Two advantages of our work over related work are the following. The hierarchical style of concurrent parallel computers is similar to the memory model used in this paper. In our approach, each analysis result is assigned a type derivation (serves as a correctness proof).

Fun with semirings

Describing a problem using classical linear algebra is a very well-known problem-solving technique. If your question can be formulated as a question about real or complex matrices, then the answer can often be found by standard techniques. It's less well-known that very similar techniques still apply where instead of real or complex numbers we have a closed semiring, which is a structure with some analogue of addition and multiplication that need not support subtraction or division. We define a typeclass in Haskell for describing closed semirings, and implement a few functions for manipulating matrices and polynomials over them. We then show how these functions can be used to calculate transitive closures, find shortest or longest or widest paths in a graph, analyse the data flow of imperative programs, optimally pack knapsacks, and perform discrete event simulations, all by just providing an appropriate underlying closed semiring.

Verification of Imperative Programs by Constraint Logic Program Transformation

We present a method for verifying partial correctness properties of imperative programs that manipulate integers and arrays by using techniques based on the transformation of constraint logic programs (CLP). We use CLP as a metalanguage for representing imperative programs, their executions, and their properties. First, we encode the correctness of an imperative program, say prog, as the negation of a predicate 'incorrect' defined by a CLP program T. By construction, 'incorrect' holds in the least model of T if and only if the execution of prog from an initial configuration eventually halts in an error configuration. Then, we apply to program T a sequence of transformations that preserve its least model semantics. These transformations are based on well-known transformation rules, such as unfolding and folding, guided by suitable transformation strategies, such as specialization and generalization. The objective of the transformations is to derive a new CLP program TransfT where the predicate 'incorrect' is defined either by (i) the fact 'incorrect.' (and in this case prog is not correct), or by (ii) the empty set of clauses (and in this case prog is correct). In the case where we derive a CLP program such that neither (i) nor (ii) holds, we iterate the transformation. Since the problem is undecidable, this process may not terminate. We show through examples that our method can be applied in a rather systematic way, and is amenable to automation by transferring to the field of program verification many techniques developed in the field of program transformation.

Modular Construction of Shape-Numeric Analyzers

The aim of static analysis is to infer invariants about programs that are precise enough to establish semantic properties, such as the absence of run-time errors. Broadly speaking, there are two major branches of static analysis for imperative programs. Pointer and shape analyses focus on inferring properties of pointers, dynamically-allocated memory, and recursive data structures, while numeric analyses seek to derive invariants on numeric values. Although simultaneous inference of shape-numeric invariants is often needed, this case is especially challenging and is not particularly well explored. Notably, simultaneous shape-numeric inference raises complex issues in the design of the static analyzer itself. In this paper, we study the construction of such shape-numeric, static analyzers. We set up an abstract interpretation framework that allows us to reason about simultaneous shape-numeric properties by combining shape and numeric abstractions into a modular, expressive abstract domain. Such a modular structure is highly desirable to make its formalization and implementation easier to do and get correct. To achieve this, we choose a concrete semantics that can be abstracted step-by-step, while preserving a high level of expressiveness. The structure of abstract operations (i.e., transfer, join, and comparison) follows the structure of this semantics. The advantage of this construction is to divide the analyzer in modules and functors that implement abstractions of distinct features.

Refinement algebra with dual operator

Algebras of imperative programming languages have been successful in reasoning about programs. In general an algebra of programs is an algebraic structure with programs as elements and with program compositions (sequential composition, choice, skip) as algebra operations. Various versions of these algebras were introduced to model partial correctness, total correctness, refinement, demonic choice, and other aspects. We introduce here an algebra which can be used to model total correctness, refinement, demonic and angelic choice. The basic model of our algebra are monotonic Boolean transformers (monotonic functions from a Boolean algebra to itself).

Compiling Scilab to high performance embedded multicore systems

The mapping process of high performance embedded applications to today’s multiprocessor system-on-chip devices suffers from a complex toolchain and programming process. The problem is the expression of parallelism with a pure imperative programming language, which is commonly C. This traditional approach limits the mapping, partitioning and the generation of optimized parallel code, and consequently the achievable performance and power consumption of applications from different domains. The Architecture oriented paraLlelization for high performance embedded Multicore systems using scilAb (ALMA) European project aims to bridge these hurdles through the introduction and exploitation of a Scilab-based toolchain which enables the efficient mapping of applications on multiprocessor platforms from a high level of abstraction. The holistic solution of the ALMA toolchain allows the complexity of both the application and the architecture to be hidden, which leads to better acceptance, reduced development cost, and shorter time-to-market. Driven by the technology restrictions in chip design, the end of exponential growth of clock speeds and an unavoidable increasing request of computing performance, ALMA is a fundamental step forward in the necessary introduction of novel computing paradigms and methodologies.

Imperative programs as proofs via game semantics

Game semantics extends the Curry–Howard isomorphism to a three-way correspondence: proofs, programs, strategies. But the universe of strategies goes beyond intuitionistic logics and lambda calculus, to capture stateful programs. In this paper we describe a logical counterpart to this extension, in which proofs denote such strategies. The system is expressive: it contains all of the connectives of Intuitionistic Linear Logic, and first-order quantification. Use of Lairdʼs sequoid operator allows proofs with imperative behaviour to be expressed. Thus, we can embed first-order Intuitionistic Linear Logic into this system, Polarized Linear Logic, and an imperative total programming language.The proof system has a tight connection with a simple game model, where games are forests of plays. Formulas are modelled as games, and proofs as history-sensitive winning strategies. We provide a strong full completeness result with respect to this model: each finitary strategy is the denotation of a unique analytic (cut-free) proof. Infinite strategies correspond to analytic proofs that are infinitely deep. Thus, we can normalise proofs, via the semantics.

Rely-guarantee references for refinement types over aliased mutable data

Reasoning about side effects and aliasing is the heart of verifying imperative programs. Unrestricted side effects through one reference can invalidate assumptions about an alias. We present a new type system approach to reasoning about safe assumptions in the presence of aliasing and side effects, unifying ideas from reference immutability type systems and rely-guarantee program logics. Our approach, rely-guarantee references, treats multiple references to shared objects similarly to multiple threads in rely-guarantee program logics. We propose statically associating rely and guarantee conditions with individual references to shared objects. Multiple aliases to a given object may coexist only if the guarantee condition of each alias implies the rely condition for all other aliases. We demonstrate that existing reference immutability type systems are special cases of rely-guarantee references. In addition to allowing precise control over state modification, rely-guarantee references allow types to depend on mutable data while still permitting flexible aliasing. Dependent types whose denotation is stable over the actions of the rely and guarantee conditions for a reference and its data will not be invalidated by any action through any alias. We demonstrate this with refinement (subset) types that may depend on mutable data. As a special case, we derive the first reference immutability type system with dependent types over immutable data. We show soundness for our approach and describe experience using rely-guarantee references in a dependently-typed monadic DSL in Coq.

Apple-CORE: Harnessing general-purpose many-cores with hardware concurrency management

To harness the potential of CMPs for scalable, energy-efficient performance in general-purpose computers, the Apple-CORE project has co-designed a general machine model and concurrency control interface with dedicated hardware support for concurrency management across multiple cores. Its SVP interface combines dataflow synchronisation with imperative programming, towards the efficient use of parallelism in general-purpose workloads. Its implementation in hardware provides logic able to coordinate single-issue, in-order multi-threaded RISC cores into computation clusters on chip, called Microgrids. In contrast with the traditional “accelerator” approach, Microgrids are components in distributed systems on chip that consider both clusters of small cores and optional, larger sequential cores as system services shared between applications. The key aspects of the design are asynchrony, i.e. the ability to tolerate irregular long latencies on chip, a scale-invariant programming model, a distributed chip resource model, and the transparent performance scaling of a single program binary code across multiple cluster sizes. This article describes the execution model, the core micro-architecture, its realization in a many-core, general-purpose processor chip and its software environment. This article also presents cycle-accurate simulation results for various key algorithmic and cryptographic kernels. The results show good efficiency in terms of the utilisation of hardware despite the high-latency memory accesses and good scalability across relatively large clusters of cores.

Matlab Toolbox for RF Receiver Modeling

In this paper a novel RF receiver modeling approach is presented. The novelty consists in the usage of the object oriented programming instead of the usual imperative programming. Classes were defined for entities as signal, non-ideality and RF/analog block, in order to achieve a basic RF receiver model. The main circuit non-idealities were identified, non-ideality parameters and their analytical models were encapsulated into classes. The effectiveness of the proposed modeling approach was demonstrated by developing in MATLAB a fairly complete model of a direct conversion receiver.

Matrix Code

Matrix Code gives imperative programming a mathematical semantics and heuristic power comparable in quality to functional and logic programming. A program in Matrix Code is developed incrementally from a specification in pre/post-condition form. The computations of a code matrix are characterized by powers of the matrix when it is interpreted as a transformation in a space of vectors of logical conditions. Correctness of a code matrix is expressed in terms of a fixpoint of the transformation. The abstract machine for Matrix Code is the dual-state machine, which we present as a variant of the classical finite-state machine.

Access-based abstract memory localization in static analysis

On-the-fly localization of abstract memory states is vital for economical abstract interpretation of imperative programs. Such localization is sometimes called “abstract garbage collection” or “framing”. In this article we present a new memory localization technique that is more effective than the conventional reachability-based approach. Our technique is based on a key observation that collecting the reachable memory parts is too conservative and the accessed parts are usually tiny subsets of the reachable part. Our technique first estimates, by an efficient pre-analysis, which parts of input states will be accessed during the analysis of each code block. Then the main analysis uses the access-set results to trim the memory entries before analyzing code blocks. In experiments with an industrial-strength global C static analyzer, the technique is applied right before analyzing each procedure’s body and reduces the average analysis time and memory by 92.1% and 71.2%, respectively, without sacrificing the analysis precision.In addition, we present three extensions of access-based localization: (1) we generalize the idea and apply the localization more frequently such as at loop bodies and basic blocks as well as procedure bodies, additionally reducing analysis time by an average of 31.8%; (2) we present a technique to mitigate a performance problem of localization in handling recursive procedures, and show that this extension improves the average analysis time by 42%; (3) we show how to incorporate the access-based localization into relational numeric analyses.