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2015 ACM SIGPLAN International Conference on Generative Programming: Concepts and Experiences (GPCE 2015), October 26–27, 2015, Pittsburgh, PA, USA

GPCE 2015 – Proceedings

Contents - Abstracts - Authors
Title Page

Message from the Chairs

The Next-Generation In-Stadium Experience (Keynote)
Priya Narasimhan, Utsav Drolia, Jiaqi Tan, Nathan D. Mickulicz, and Rajeev Gandhi
(Carnegie Mellon University, USA)
YinzCam is a cloud-hosted service that provides sports fans with real-time scores, news, photos, statistics, live radio, streaming video, etc., on their mobile devices. YinzCam’s infrastructure is currently hosted on Amazon Web Services (AWS) and supports over 30 million installs of the official mobile apps of 140+ NHL/NFL/NBA/NRL/NCAA sports teams and venues. YinzCam’s workload is necessarily multi-modal (e.g., pre-game, in-game, post-game, game-day, non-gameday), with normal game-time traffic being twenty-fold of that on non-game days. This paper describes the evolution of YinzCam’s production architecture and distributed infrastructure, from its beginnings in 2009, when it was used to support thousands of concurrent users, to today’s system that supports millions of concurrent users on any game day. We also discuss key new opportunities to improve the fan experience inside the stadium of the future, without impacting the available bandwidth, by crowd-sourcing the thousands of mobile devices that are in fans’ hands inside these venues. We present Krowd, a novel distributed key-value store for promoting efficient content sharing, discovery and retrieval across the mobile devices inside a stadium. We present CHIPS, a system that ensures that users’ privacy is maintained while their devices participate in the crowdsourced infrastructure.

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Shallow Embedding of DSLs via Online Partial Evaluation
Roland Leißa, Klaas Boesche, Sebastian Hack, Richard Membarth, and Philipp Slusallek
(Saarland University, Germany; German Research Center for Artificial Intelligence, Germany)
This paper investigates shallow embedding of DSLs by means of online partial evaluation. To this end, we present a novel online partial evaluator for continuation-passing style languages. We argue that it has, in contrast to prior work, a predictable termination policy that works well in practice. We present our approach formally using a continuation-passing variant of PCF and prove its termination properties. We evaluate our technique experimentally in the field of visual and high-performance computing and show that our evaluator produces highly specialized and efficient code for CPUs as well as GPUs that matches the performance of hand-tuned expert code.

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Almost First-Class Language Embedding: Taming Staged Embedded DSLs
Maximilian Scherr and Shigeru Chiba
(University of Tokyo, Japan)
Embedded domain-specific languages (EDSLs), inheriting a general-purpose language's features as well as look-and-feel, have traditionally been second-class or rather non-citizens in terms of host-language design. This makes sense when one regards them to be on the same level as traditional, non-EDSL library interfaces. However, this equivalence only applies to the simplest of EDSLs. In this paper we illustrate why this is detrimental when moving on to EDSLs that employ staging, i.e. program reification, by example of various issues that affect authors and users alike. We believe that if EDSLs are to be considered a reliable, language-like interface abstraction, they require exceptional attention and design scrutiny. Instead of unenforceable conventions, we advocate the acceptance of EDSLs as proper, i.e. almost first-class, citizens while retaining most advantages of pure embeddings. As a small step towards this goal, we present a pragmatic framework prototype for Java. It is based on annotations that explicate and document membership to explicit EDSL entities. In a nutshell, our framework identifies (annotated) method calls and field accesses as EDSL terms and dynamically constructs an abstract-syntax representation, which is eventually passed to a semantics-defining back end implemented by the EDSL author.

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Generating Safe Boundary APIs between Typed EDSLs and Their Environments
Bob Reynders, Dominique Devriese, and Frank Piessens
(iMinds, Belgium; KU Leuven, Belgium)
Embedded domain specific languages (EDSLs) are used to represent special-purpose code in a general-purpose language and they are used for applications like vector calculations and run-time code generation. Often, code in an EDSL is compiled to a target (e.g. GPU languages, JVM bytecode, assembly, JavaScript) and needs to interface with other code that is available at that level but uses other data representations or calling conventions.
We present an approach for safely making available such APIs in a typed EDSL, guaranteeing correct conversions between data representations and the respect for calling conventions. When the code being interfaced with is the result of static compilation of host language code, we propose a way to auto-generate the needed boilerplate using meta-programming. We instantiate our technique with JavaScript as the target language, JS-Scala as the EDSL, Scala.js as the static compiler and Scala macros to generate the boilerplate, but our design is more generally applicable. We provide evidence of usefulness of our approach through a prototype implementation that we have applied in a non-trivial code base.

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An Empirical Study on Configuration-Related Issues: Investigating Undeclared and Unused Identifiers
Flávio Medeiros, Iran Rodrigues, Márcio Ribeiro, Leopoldo Teixeira, and Rohit Gheyi
(Federal University of Campina Grande, Brazil; Federal University of Alagoas, Brazil; Federal University of Pernambuco, Brazil)
The variability of configurable systems may lead to configuration-related issues (i.e., faults and warnings) that appear only when we select certain configuration options. Previous studies found that issues related to configurability are harder to detect than issues that appear in all configurations, because variability increases the complexity. However, little effort has been put into understanding configuration-related faults (e.g., undeclared functions and variables) and warnings (e.g., unused functions and variables). To better understand the peculiarities of configuration-related undeclared/unused variables and functions, in this paper we perform an empirical study of 15 systems to answer research questions related to how developers introduce these issues, the number of configuration options involved, and the time that these issues remain in source files. To make the analysis of several projects feasible, we propose a strategy that minimizes the initial setup problems of variability-aware tools. We detect and confirm 2 undeclared variables, 14 undeclared functions, 16 unused variables, and 7 unused functions related to configurability. We submit 30 patches to fix issues not fixed by developers. Our findings support the effectiveness of sampling (i.e., analysis of only a subset of valid configurations) because most issues involve two or less configuration options. Nevertheless, by analyzing the version history of the projects, we observe that a number of issues remain in the code for several years. Furthermore, the corpus of undeclared/unused variables and functions gathered is a valuable source to study these issues, compare sampling algorithms, and test and improve variability-aware tools.

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Analysing the Kconfig Semantics and Its Analysis Tools
Sascha El-Sharkawy, Adam Krafczyk, and Klaus Schmid
(University of Hildesheim, Germany)
The Linux kernel is often used as a real world case study to demonstrate novel Software Product Line Engineering research methods. An important point in this is often the analysis of the Kconfig semantics. However, we detected that the semantics of Kconfig is rather unclear and has many special cases, which are not documented in its short specification. We performed a systematic analysis to uncover the correct behaviour of Kconfig and present the results, which are necessary for applying semantically correct analyses. Further, we analyse existing analysis tools of the research community whether they are aware of the correct semantics of Kconfig. These analyses can be used for improving existing analysis tools as well as decision support for selecting an appropriate tool for a specific analysis. In summary we contribute to a better understanding of Kconfig in the research community to improve the validity of evaluations based on Linux.

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Migrating Large Object-Oriented Applications into Component-Based Ones: Instantiation and Inheritance Transformation
Zakarea Alshara, Abdelhak-Djamel Seriai, Chouki Tibermacine, Hinde Lilia Bouziane, Christophe Dony, and Anas Shatnawi
(LIRMM, France; CNRS, France; University of Montpellier, France)
Large object-oriented applications have complex and numerous dependencies, and usually do not have explicit software architectures. Therefore they are hard to maintain, and parts of them are difficult to reuse. Component-based development paradigm emerged for improving these aspects and for supporting effective maintainability and reuse. It provides better understandability through a high-level architecture view of the application. Thereby migrating object-oriented applications to component-based ones will contribute to improve these characteristics (maintainability and reuse). In this paper, we propose an approach to automatically transform object-oriented applications to component-based ones. More particularly, the input of the approach is the result provided by software architecture recovery: a component-based architecture description. Then, our approach transforms the object-oriented source code in order to produce deployable components. We focus in this paper on the transformation of source code related to instantiation and inheritance dependencies between classes that are in different components. We experimented the proposed solution in the transformation of a collection of Java applications into the OSGi framework. The experimental results are discussed in this paper.

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Safer SDN Programming through Arbiter
Michael Lopez, C. Jasson Casey, Gabriel Dos Reis, and Colton Chojnacki
(Texas A&M University, USA; Flowgrammable, USA; Microsoft, USA)
Software Defined Networking (SDN) programs are written with respect to assumptions on software and hardware facilities and protocol definitions. Silent mismatches between the expected feature set and implemented feature set of SDN artifacts can easily lead to hard to debug network configurations, decreased network performance, outages, or worse, security vulnerabilities. We show how the paradigm of axiomatic programming, supported by practical dependent types, provides effective support for SDN executable specifications and verification.​

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Contract-Based General-Purpose GPU Programming
Alexey Kolesnichenko, Christopher M. Poskitt, Sebastian Nanz, and Bertrand Meyer
(ETH Zurich, Switzerland)
Using GPUs as general-purpose processors has revolutionized parallel computing by offering, for a large and growing set of algorithms, massive data-parallelization on desktop machines. An obstacle to widespread adoption, however, is the difficulty of programming them and the low-level control of the hardware required to achieve good performance. This paper suggests a programming library, SafeGPU, that aims at striking a balance between programmer productivity and performance, by making GPU data-parallel operations accessible from within a classical object-oriented programming language. The solution is integrated with the design-by-contract approach, which increases confidence in functional program correctness by embedding executable program specifications into the program text. We show that our library leads to modular and maintainable code that is accessible to GPGPU non-experts, while providing performance that is comparable with hand-written CUDA code. Furthermore, runtime contract checking turns out to be feasible, as the contracts can be executed on the GPU.

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Inverse Macro in Scala
Hiroshi Yamaguchi and Shigeru Chiba
(University of Tokyo, Japan)
We propose a new variant of typed syntactic macro systems named inverse macro, which improves the expressiveness of macro systems. The inverse macro system enables to implement operators with complex side-effects, such as lazy operators and delimited continuation operators, which are beyond the power of existing macro systems. We have implemented the inverse macro system as an extension to Scala 2.11. We also show the expressiveness of the inverse macro system by comparing two versions of shift/reset, bundled in Scala 2.11 and implemented with the inverse macro system.

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Towards Tool Support for Spreadsheet-Based Domain-Specific Languages
Sorin Adam and Ulrik Pagh Schultz
(University of Southern Denmark, Denmark)
Spreadsheets are commonly used by non-programmers to store data in a structured form, this data can in some cases be considered to be a program in a domain-specific language (DSL). Unlike ordinary text-based domain-specific languages, there is however currently no formalism for expressing the syntax of such spreadsheet-based DSLs (SDSLs), and there is no tool support for automatically generating language infrastructure such as parsers and IDE support. In this paper we define a simple notion of two-dimensional grammars for SDSLs, and show how such grammars can be used for automatically generating parsers that extract structured data from a spreadsheet in the form of an AST. We demonstrate automatic generation of parsers for a number of examples, including the questionnaire DSL from LWC2014 and a DSL for writing safety specifications.

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Native-2-Native: Automated Cross-Platform Code Synthesis from Web-Based Programming Resources
Antuan Byalik, Sanchit Chadha, and Eli Tilevich
(Virginia Tech, USA)
For maximal market penetration, popular mobile applications are typically supported on all major platforms, including Android and iOS. Despite the vast differences in the look-and-feel of major mobile platforms, applications running on these platforms in essence provide the same core functionality. As an application is maintained and evolved, the resulting changes must be replicated on all the supported platforms, a tedious and error-prone programming process. Existing automated source-to-source translation tools prove inadequate due to the structural and idiomatic differences in how functionalities are expressed across major platforms.
In this paper, we present a new approach---Native-2-Native---that automatically synthesizes code for a mobile application to make use of native resources on one platform, based on the equivalent program transformations performed on another platform. First, the programmer modifies a mobile application's Android version to make use of some native resource, with a plugin capturing code changes. Based on the changes, the system then parameterizes a web search query over popular programming resources (e.g., Google Code, StackOverflow, etc.), to discover equivalent iOS code blocks with the closest similarity to the programmer-written Android code. The discovered iOS code block is then presented to the programmer as an automatically synthesized Swift source file to further fine-tune and subsequently integrate in the mobile application's iOS version. Our evaluation, enhancing mobile applications to make use of common native resources, shows that the presented approach can correctly synthesize more than 86% of Swift code for the subject applications' iOS versions.

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CLOP: A Multi-stage Compiler to Seamlessly Embed Heterogeneous Code
Dmitri Makarov and Matthias Hauswirth
(University of Lugano, Switzerland)
Heterogeneous programming complicates software development. We present CLOP, a platform that embeds code targeting heterogeneous compute devices in a convenient and clean way, allowing unobstructed data flow between the host code and the devices, reducing the amount of source code by an order of magnitude. The CLOP compiler uses the standard facilities of the D programming language to generate code strictly at compile-time. In this paper we describe the CLOP language and the CLOP compiler implementation.

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Composing Code Generators for C&C ADLs with Application-Specific Behavior Languages (Tool Demonstration)
Jan Oliver Ringert, Bernhard Rumpe, and Andreas Wortmann
(Tel Aviv University, Israel; RWTH Aachen University, Germany)
Modeling software systems as component & connector architectures with application-specific behavior modeling languages enables domain experts to describe each component behavior with the most appropriate language. Generating executable systems for such language aggregates requires composing appropriate code generators for the participating languages. Previous work on code generator composition either focuses on white-box integration based on code generator internals or requires extensive handcrafting of integration code. We demonstrate an approach to black-box generator composition for architecture description languages that relies on explicit interfaces and exploits the encapsulation of components. This approach is implemented for the architecture modeling framework MontiArcAutomaton and has been evaluated in various contexts. Ultimately, black-box code generator composition facilitates development of code generators for architecture description languages with embedded behavior languages and increases code generator reuse.

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Orchestrating Masses of Sensors: A Design-Driven Development Approach
Milan Kabáč and Charles Consel
(INRIA, France; University of Bordeaux, France)
This paper proposes a design-driven development approach that is dedicated to the domain of orchestration of masses of sensors. The developer declares what an application does using a domain-specific language (DSL). Our compiler processes domain-specific declarations to generate a customized programming framework that guides and supports the programming phase.

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Generating Reactive Programs for Graphical User Interfaces from Multi-way Dataflow Constraint Systems
Gabriel Foust, Jaakko Järvi, and Sean Parent
(Texas A&M University, USA; Adobe, USA)
For a GUI to remain responsive, it must be able to schedule lengthy tasks to be executed asynchronously. In the traditional approach to GUI implementation--writing functions to handle individual user events--asynchronous programming easily leads to defects. Ensuring that all data dependencies are respected is difficult when new events arrive while prior events are still being handled. Reactive programming techniques, gaining popularity in GUI programming, help since they make data dependencies explicit and enforce them automatically as variables' values change. However, data dependencies in GUIs usually change along with its state. Reactive programming must therefore describe a GUI as a collection of many reactive programs, whose interaction the programmer must explicitly coordinate. This paper presents a declarative approach for GUI programming that relieves the programmer from coordinating asynchronous computations. The approach is based on our prior work on "property models", where GUI state is maintained by a dataflow constraint system. A property model responds to user events by atomically constructing new data dependencies and scheduling asynchronous computations to enforce those dependencies. In essence, a property model dynamically generates a reactive program, adding to it as new events occur. The approach gives the following guarantee: the same sequence of events produces the same results, regardless of the timing of those events.

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POP-PL: A Patient-Oriented Prescription Programming Language
Spencer P. Florence, Bruke Fetscher, Matthew Flatt, William H. Temps, Tina Kiguradze, Dennis P. West, Charlotte Niznik, Paul R. Yarnold, Robert Bruce Findler, and Steven M. Belknap
(Northwestern University, USA; University of Utah, USA; Optimal Data Analysis, USA)
Medical professionals have long used algorithmic thinking to describe and implement health care processes without the benefit of the conceptual framework provided by a programming language. Instead, medical algorithms are expressed using English, flowcharts, or data tables. This results in prescriptions that are difficult to understand, hard to debug, and awkward to reuse.
This paper reports on the design and evaluation of a domain-specific programming language, POP-PL for expressing medical algorithms. The design draws on the experience of researchers in two disciplines, programming languages and medicine. The language is based around the idea that programs and humans have complementary strengths, that when combined can make for safer, more accurate performance of prescriptions.
We implemented a prototype of our language and evaluated its design by writing prescriptions in the new language and administering a usability survey to medical professionals. This formative evaluation suggests that medical prescriptions can be conveyed by a programming language's mode of expression and provides useful information for refining the language. Analysis of the survey results suggests that medical professionals can understand and correctly modify programs in POP-PL.

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Lightweight, Generative Variant Exploration for High-Performance Graphics Applications
Kai Selgrad, Alexander Lier, Franz Köferl, Marc Stamminger, and Daniel Lohmann
(University of Erlangen-Nuremberg, Germany)
Rendering performance is an everlasting goal of computer graphics and significant driver for advances in both, hardware architecture and algorithms. Thereby, it has become possible to apply advanced computer graphics technology even in low-cost embedded appliances, such as car instruments. Yet, to come up with an efficient implementation, developers have to put enormous efforts into hardware/problem-specific tailoring, fine-tuning, and domain exploration, which requires profound expert knowledge. If a good solution has been found, there is a high probability that it does not work as well with other architectures or even the next hardware generation. Generative DSL-based approaches could mitigate these efforts and provide for an efficient exploration of algorithmic variants and hardware-specific tuning ideas. However, in vertically organized industries, such as automotive, suppliers are reluctant to introduce these techniques as they fear loss of control, high introduction costs, and additional constraints imposed by the OEM with respect to software and tool-chain certification. Moreover, suppliers do not want to share their generic solutions with the OEM, but only concrete instances. To this end, we propose a light-weight and incremental approach for meta programming of graphics applications. Our approach relies on an existing formulation of C-like languages that is amenable to meta programming, which we extend to become a lightweight language to combine algorithmic features. Our method provides a concise notation for meta programs and generates easily sharable output in the appropriate C-style target language.

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Generative Software Product Line Development using Variability-Aware Design Patterns
Christoph Seidl, Sven Schuster, and Ina Schaefer
(TU Braunschweig, Germany)
Software Product Lines (SPLs) are an approach to reuse in-the-large that models a set of closely related software systems in terms of commonalities and variabilities. Design patterns are best practices for addressing recurring design problems in object-oriented source code. In the practice of implementing an SPL, instances of certain design patterns are employed to handle variability, which makes these "variability-aware design patterns" a best practice for SPL design. However, there currently is no dedicated method for proactively developing SPL using design patterns suitable for realizing variable functionality. In this paper, we present a method to perform generative SPL development with design patterns. We use role models to capture design patterns and their relation to a variability model. We further allow mapping of individual design pattern roles to elements of realization artifacts to be generated (e.g., classes, methods) and check the conformance of the realization with the specification of the pattern. With this method, we support proactive development of SPL using design patterns to apply best practices for the realization of variability. We present an implementation of our approach within the Eclipse IDE and demonstrate it within a case study.

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Addressing Metamodel Revisions in Model-Based Software Product Lines
Jaime Font, Lorena Arcega, Øystein Haugen, and Carlos Cetina
(San Jorge University, Spain; University of Oslo, Norway; Østfold University College, Norway)
Metamodels evolve over time, which can break the conformance between the models and the metamodel. Model migration strategies aim to co-evolve models and metamodels together, but their application is not fully automatizable and is thus cumbersome and error prone. We introduce the Variable MetaModel (VMM) strategy to address the evolution of the reusable model assets of a model-based Software Product Line. The VMM strategy applies variability modeling ideas to express the evolution of the metamodel in terms of commonalities and variabilities. When the metamodel evolves, the models continue to conform to the VMM, avoiding the need for migration. We have applied both the traditional migration strategy and the VMM strategy to a retrospective case study that includes 13 years of evolution of our industrial partner, an induction hobs manufacturer. The comparison between the two strategies shows better results for the VMM strategy in terms of model indirection, automation, and trust leak.

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Modular Interpreters for the Masses: Implicit Context Propagation using Object Algebras
Pablo Inostroza and Tijs van der Storm
(CWI, Netherlands)
Modular interpreters have the potential to achieve component-based language development: instead of writing language interpreters from scratch, they can be assembled from reusable, semantic building blocks. Unfortunately, traditional language interpreters are hard to extend because different language constructs may require different interpreter signatures. For instance, arithmetic interpreters produce a value without any context information, whereas binding constructs require an additional environment. In this paper, we present a practical solution to this problem based on implicit context propagation. By structuring denotational-style interpreters as Object Algebras, base interpreters can be retroactively lifted into new interpreters that have an extended signature. The additional parameters are implicitly propagated behind the scenes, through the evaluation of the base interpreter. Interpreter lifting enables a flexible style of component-based language development. The technique works in mainstream object-oriented languages, does not sacrifice type safety or separate compilation, and can be easily automated. We illustrate implicit context propagation using a modular definition of Featherweight Java and its extension to support side-effects.

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Model Querying with Query Models
Carlos Noguera and Viviane Jonckers
(Vrije Universiteit Brussel, Belgium)
Model querying is an integral part of Model-Driven Engineering. Developers query models when specifying model transformations, when defining model constraints, or simply when they need to extract some information from the model. Model queries are often specified in a general-purpose programming language, with developers just navigating models through their programming interfaces. OCL is the best known model query language, and while successful, it is difficult to express complex structural properties featured in target model elements. In this paper we describe a model query facility that aims at easing the description of structural features in a query. In our approach, developers model their queries by reusing fragments of the target model to specify the invariant parts of the template, augmented with variables and special relations to specify what can vary. The query itself conforms to a meta-model that extends the meta-model under-query. By reusing the queried meta- model developers can reduce the mental overhead that comes from using a different language to specify the queries. We have developed a proof of concept tool for the Eclipse Modeling Framework (EMF) that (1) generates a query meta-model from a target meta- model, (2) allows the construction of queries using a graphical, graph-based editor and (3) executes the queries by translating them to a set of logic predicates that are then evaluated using an extension of the logic-based query language Ekeko.

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