Despite the presence of garbage collection in managed languages like JavaScript, memory leaks remain a serious problem. In the context of web applications, these leaks are especially pervasive and difficult to debug. Web application memory leaks can take many forms, including failing to dispose of unneeded event listeners, repeatedly injecting iframes and CSS files, and failing to call cleanup routines in third-party libraries. Leaks degrade responsiveness by increasing GC frequency and overhead, and can even lead to browser tab crashes by exhausting available memory. Because previous leak detection approaches designed for conventional C, C++ or Java applications are ineffective in the browser environment, tracking down leaks currently requires intensive manual effort by web developers. This paper introduces BLeak (Browser Leak debugger), the first system for automatically debugging memory leaks in web applications. BLeak's algorithms leverage the observation that in modern web applications, users often repeatedly return to the same (approximate) visual state (e.g., the inbox view in Gmail). Sustained growth between round trips is a strong indicator of a memory leak. To use BLeak, a developer writes a short script (17-73 LOC on our benchmarks) to drive a web application in round trips to the same visual state. BLeak then automatically generates a list of leaks found along with their root causes, ranked by return on investment. Guided by BLeak, we identify and fix over 50 memory leaks in popular libraries and apps including Airbnb, AngularJS, Google Analytics, Google Maps SDK, and jQuery. BLeak's median precision is 100%; fixing the leaks it identifies reduces heap growth by an average of 94%, saving from 0.5 MB to 8 MB per round trip. We believe BLeak's approach to be broadly applicable beyond web applications, including to GUI applications on desktop and mobile platforms.
{"title":"BLeak: automatically debugging memory leaks in web applications","authors":"J. Vilk, E. Berger","doi":"10.1145/3192366.3192376","DOIUrl":"https://doi.org/10.1145/3192366.3192376","url":null,"abstract":"Despite the presence of garbage collection in managed languages like JavaScript, memory leaks remain a serious problem. In the context of web applications, these leaks are especially pervasive and difficult to debug. Web application memory leaks can take many forms, including failing to dispose of unneeded event listeners, repeatedly injecting iframes and CSS files, and failing to call cleanup routines in third-party libraries. Leaks degrade responsiveness by increasing GC frequency and overhead, and can even lead to browser tab crashes by exhausting available memory. Because previous leak detection approaches designed for conventional C, C++ or Java applications are ineffective in the browser environment, tracking down leaks currently requires intensive manual effort by web developers. This paper introduces BLeak (Browser Leak debugger), the first system for automatically debugging memory leaks in web applications. BLeak's algorithms leverage the observation that in modern web applications, users often repeatedly return to the same (approximate) visual state (e.g., the inbox view in Gmail). Sustained growth between round trips is a strong indicator of a memory leak. To use BLeak, a developer writes a short script (17-73 LOC on our benchmarks) to drive a web application in round trips to the same visual state. BLeak then automatically generates a list of leaks found along with their root causes, ranked by return on investment. Guided by BLeak, we identify and fix over 50 memory leaks in popular libraries and apps including Airbnb, AngularJS, Google Analytics, Google Maps SDK, and jQuery. BLeak's median precision is 100%; fixing the leaks it identifies reduces heap growth by an average of 94%, saving from 0.5 MB to 8 MB per round trip. We believe BLeak's approach to be broadly applicable beyond web applications, including to GUI applications on desktop and mobile platforms.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87097867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
If-conversion is a fundamental technique for vectorization. It accounts for the fact that in a SIMD program, several targets of a branch might be executed because of divergence. Especially for irregular data-parallel workloads, it is crucial to avoid if-converting non-divergent branches to increase SIMD utilization. In this paper, we present partial linearization, a simple and efficient if-conversion algorithm that overcomes several limitations of existing if-conversion techniques. In contrast to prior work, it has provable guarantees on which non-divergent branches are retained and will never duplicate code or insert additional branches. We show how our algorithm can be used in a classic loop vectorizer as well as to implement data-parallel languages such as ISPC or OpenCL. Furthermore, we implement prior vectorizer optimizations on top of partial linearization in a more general way. We evaluate the implementation of our algorithm in LLVM on a range of irregular data analytics kernels, a neutronics simulation benchmark and NAB, a molecular dynamics benchmark from SPEC2017 on AVX2, AVX512, and ARM Advanced SIMD machines and report speedups of up to 146 % over ICC, GCC and Clang O3.
{"title":"Partial control-flow linearization","authors":"Simon Moll, Sebastian Hack","doi":"10.1145/3192366.3192413","DOIUrl":"https://doi.org/10.1145/3192366.3192413","url":null,"abstract":"If-conversion is a fundamental technique for vectorization. It accounts for the fact that in a SIMD program, several targets of a branch might be executed because of divergence. Especially for irregular data-parallel workloads, it is crucial to avoid if-converting non-divergent branches to increase SIMD utilization. In this paper, we present partial linearization, a simple and efficient if-conversion algorithm that overcomes several limitations of existing if-conversion techniques. In contrast to prior work, it has provable guarantees on which non-divergent branches are retained and will never duplicate code or insert additional branches. We show how our algorithm can be used in a classic loop vectorizer as well as to implement data-parallel languages such as ISPC or OpenCL. Furthermore, we implement prior vectorizer optimizations on top of partial linearization in a more general way. We evaluate the implementation of our algorithm in LLVM on a range of irregular data analytics kernels, a neutronics simulation benchmark and NAB, a molecular dynamics benchmark from SPEC2017 on AVX2, AVX512, and ARM Advanced SIMD machines and report speedups of up to 146 % over ICC, GCC and Clang O3.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72894933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yu-Fang Chen, Matthias Heizmann, Ondřej Lengál, Yong Li, M. Tsai, Andrea Turrini, Lijun Zhang
In 2014, Heizmann et al. proposed a novel framework for program termination analysis. The analysis starts with a termination proof of a sample path. The path is generalized to a Büchi automaton (BA) whose language (by construction) represents a set of terminating paths. All these paths can be safely removed from the program. The removal of paths is done using automata difference, implemented via BA complementation and intersection. The analysis constructs in this way a set of BAs that jointly "cover" the behavior of the program, thus proving its termination. An implementation of the approach in Ultimate Automizer won the 1st place in the Termination category of SV-COMP 2017. In this paper, we exploit advanced automata-based algorithms and propose several non-trivial improvements of the framework. To alleviate the complementation computation for BAs---one of the most expensive operations in the framework---, we propose a multi-stage generalization construction. We start with generalizations producing subclasses of BAs (such as deterministic BAs) for which efficient complementation algorithms are known, and proceed to more general classes only if necessary. Particularly, we focus on the quite expressive subclass of semideterministic BAs and provide an improved complementation algorithm for this class. Our experimental evaluation shows that the proposed approach significantly improves the power of termination checking within the Ultimate Automizer framework.
{"title":"Advanced automata-based algorithms for program termination checking","authors":"Yu-Fang Chen, Matthias Heizmann, Ondřej Lengál, Yong Li, M. Tsai, Andrea Turrini, Lijun Zhang","doi":"10.1145/3192366.3192405","DOIUrl":"https://doi.org/10.1145/3192366.3192405","url":null,"abstract":"In 2014, Heizmann et al. proposed a novel framework for program termination analysis. The analysis starts with a termination proof of a sample path. The path is generalized to a Büchi automaton (BA) whose language (by construction) represents a set of terminating paths. All these paths can be safely removed from the program. The removal of paths is done using automata difference, implemented via BA complementation and intersection. The analysis constructs in this way a set of BAs that jointly \"cover\" the behavior of the program, thus proving its termination. An implementation of the approach in Ultimate Automizer won the 1st place in the Termination category of SV-COMP 2017. In this paper, we exploit advanced automata-based algorithms and propose several non-trivial improvements of the framework. To alleviate the complementation computation for BAs---one of the most expensive operations in the framework---, we propose a multi-stage generalization construction. We start with generalizations producing subclasses of BAs (such as deterministic BAs) for which efficient complementation algorithms are known, and proceed to more general classes only if necessary. Particularly, we focus on the quite expressive subclass of semideterministic BAs and provide an improved complementation algorithm for this class. Our experimental evaluation shows that the proposed approach significantly improves the power of termination checking within the Ultimate Automizer framework.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75901012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ronghui Gu, Zhong Shao, Jieung Kim, Xiongnan Wu, Jérémie Koenig, Vilhelm Sjöberg, Hao Chen, D. Costanzo, T. Ramananandro
Concurrent abstraction layers are ubiquitous in modern computer systems because of the pervasiveness of multithreaded programming and multicore hardware. Abstraction layers are used to hide the implementation details (e.g., fine-grained synchronization) and reduce the complex dependencies among components at different levels of abstraction. Despite their obvious importance, concurrent abstraction layers have not been treated formally. This severely limits the applicability of layer-based techniques and makes it difficult to scale verification across multiple concurrent layers. In this paper, we present CCAL---a fully mechanized programming toolkit developed under the CertiKOS project---for specifying, composing, compiling, and linking certified concurrent abstraction layers. CCAL consists of three technical novelties: a new game-theoretical, strategy-based compositional semantic model for concurrency (and its associated program verifiers), a set of formal linking theorems for composing multithreaded and multicore concurrent layers, and a new CompCertX compiler that supports certified thread-safe compilation and linking. The CCAL toolkit is implemented in Coq and supports layered concurrent programming in both C and assembly. It has been successfully applied to build a fully certified concurrent OS kernel with fine-grained locking.
{"title":"Certified concurrent abstraction layers","authors":"Ronghui Gu, Zhong Shao, Jieung Kim, Xiongnan Wu, Jérémie Koenig, Vilhelm Sjöberg, Hao Chen, D. Costanzo, T. Ramananandro","doi":"10.1145/3192366.3192381","DOIUrl":"https://doi.org/10.1145/3192366.3192381","url":null,"abstract":"Concurrent abstraction layers are ubiquitous in modern computer systems because of the pervasiveness of multithreaded programming and multicore hardware. Abstraction layers are used to hide the implementation details (e.g., fine-grained synchronization) and reduce the complex dependencies among components at different levels of abstraction. Despite their obvious importance, concurrent abstraction layers have not been treated formally. This severely limits the applicability of layer-based techniques and makes it difficult to scale verification across multiple concurrent layers. In this paper, we present CCAL---a fully mechanized programming toolkit developed under the CertiKOS project---for specifying, composing, compiling, and linking certified concurrent abstraction layers. CCAL consists of three technical novelties: a new game-theoretical, strategy-based compositional semantic model for concurrency (and its associated program verifiers), a set of formal linking theorems for composing multithreaded and multicore concurrent layers, and a new CompCertX compiler that supports certified thread-safe compilation and linking. The CCAL toolkit is implemented in Coq and supports layered concurrent programming in both C and assembly. It has been successfully applied to build a fully certified concurrent OS kernel with fine-grained locking.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87974004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dependently typed languages such as Coq are used to specify and verify the full functional correctness of source programs. Type-preserving compilation can be used to preserve these specifications and proofs of correctness through compilation into the generated target-language programs. Unfortunately, type-preserving compilation of dependent types is hard. In essence, the problem is that dependent type systems are designed around high-level compositional abstractions to decide type checking, but compilation interferes with the type-system rules for reasoning about run-time terms. We develop a type-preserving closure-conversion translation from the Calculus of Constructions (CC) with strong dependent pairs (Σ types)—a subset of the core language of Coq—to a type-safe, dependently typed compiler intermediate language named CC-CC. The central challenge in this work is how to translate the source type-system rules for reasoning about functions into target type-system rules for reasoning about closures. To justify these rules, we prove soundness of CC-CC by giving a model in CC. In addition to type preservation, we prove correctness of separate compilation.
{"title":"Typed closure conversion for the calculus of constructions","authors":"W. J. Bowman, Amal J. Ahmed","doi":"10.1145/3192366.3192372","DOIUrl":"https://doi.org/10.1145/3192366.3192372","url":null,"abstract":"Dependently typed languages such as Coq are used to specify and verify the full functional correctness of source programs. Type-preserving compilation can be used to preserve these specifications and proofs of correctness through compilation into the generated target-language programs. Unfortunately, type-preserving compilation of dependent types is hard. In essence, the problem is that dependent type systems are designed around high-level compositional abstractions to decide type checking, but compilation interferes with the type-system rules for reasoning about run-time terms. We develop a type-preserving closure-conversion translation from the Calculus of Constructions (CC) with strong dependent pairs (Σ types)—a subset of the core language of Coq—to a type-safe, dependently typed compiler intermediate language named CC-CC. The central challenge in this work is how to translate the source type-system rules for reasoning about functions into target type-system rules for reasoning about closures. To justify these rules, we prove soundness of CC-CC by giving a model in CC. In addition to type preservation, we prove correctness of separate compilation.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86057650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Serrano, Jurriaan Hage, Dimitrios Vytiniotis, S. P. Jones
The design space for type systems that support impredicative instantiation is extremely complicated. One needs to strike a balance between expressiveness, simplicity for both the end programmer and the type system implementor, and how easily the system can be integrated with other advanced type system concepts. In this paper, we propose a new point in the design space, which we call guarded impredicativity. Its key idea is that impredicative instantiation in an application is allowed for type variables that occur under a type constructor. The resulting type system has a clean declarative specification — making it easy for programmers to predict what will type and what will not —, allows for a smooth integration with GHC’s OutsideIn(X) constraint solving framework, while giving up very little in terms of expressiveness compared to systems like HMF, HML, FPH and MLF. We give a sound and complete inference algorithm, and prove a principal type property for our system.
{"title":"Guarded impredicative polymorphism","authors":"A. Serrano, Jurriaan Hage, Dimitrios Vytiniotis, S. P. Jones","doi":"10.1145/3192366.3192389","DOIUrl":"https://doi.org/10.1145/3192366.3192389","url":null,"abstract":"The design space for type systems that support impredicative instantiation is extremely complicated. One needs to strike a balance between expressiveness, simplicity for both the end programmer and the type system implementor, and how easily the system can be integrated with other advanced type system concepts. In this paper, we propose a new point in the design space, which we call guarded impredicativity. Its key idea is that impredicative instantiation in an application is allowed for type variables that occur under a type constructor. The resulting type system has a clean declarative specification — making it easy for programmers to predict what will type and what will not —, allows for a smooth integration with GHC’s OutsideIn(X) constraint solving framework, while giving up very little in terms of expressiveness compared to systems like HMF, HML, FPH and MLF. We give a sound and complete inference algorithm, and prove a principal type property for our system.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76672015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a data-driven technique to solve Constrained Horn Clauses (CHCs) that encode verification conditions of programs containing unconstrained loops and recursions. Our CHC solver neither constrains the search space from which a predicate's components are inferred (e.g., by constraining the number of variables or the values of coefficients used to specify an invariant), nor fixes the shape of the predicate itself (e.g., by bounding the number and kind of logical connectives). Instead, our approach is based on a novel machine learning-inspired tool chain that synthesizes CHC solutions in terms of arbitrary Boolean combinations of unrestricted atomic predicates. A CEGAR-based verification loop inside the solver progressively samples representative positive and negative data from recursive CHCs, which is fed to the machine learning tool chain. Our solver is implemented as an LLVM pass in the SeaHorn verification framework and has been used to successfully verify a large number of nontrivial and challenging C programs from the literature and well-known benchmark suites (e.g., SV-COMP).
{"title":"A data-driven CHC solver","authors":"He Zhu, Stephen Magill, S. Jagannathan","doi":"10.1145/3192366.3192416","DOIUrl":"https://doi.org/10.1145/3192366.3192416","url":null,"abstract":"We present a data-driven technique to solve Constrained Horn Clauses (CHCs) that encode verification conditions of programs containing unconstrained loops and recursions. Our CHC solver neither constrains the search space from which a predicate's components are inferred (e.g., by constraining the number of variables or the values of coefficients used to specify an invariant), nor fixes the shape of the predicate itself (e.g., by bounding the number and kind of logical connectives). Instead, our approach is based on a novel machine learning-inspired tool chain that synthesizes CHC solutions in terms of arbitrary Boolean combinations of unrestricted atomic predicates. A CEGAR-based verification loop inside the solver progressively samples representative positive and negative data from recursive CHCs, which is fed to the machine learning tool chain. Our solver is implemented as an LLVM pass in the SeaHorn verification framework and has been used to successfully verify a large number of nontrivial and challenging C programs from the literature and well-known benchmark suites (e.g., SV-COMP).","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80571432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Brandon Bohrer, Yong Kiam Tan, Stefan Mitsch, Magnus O. Myreen, André Platzer
We present VeriPhy, a verified pipeline which automatically transforms verified high-level models of safety-critical cyber-physical systems (CPSs) in differential dynamic logic (dL) to verified controller executables. VeriPhy proves that all safety results are preserved end-to-end as it bridges abstraction gaps, including: i) the gap between mathematical reals in physical models and machine arithmetic in the implementation, ii) the gap between real physics and its differential-equation models, and iii) the gap between nondeterministic controller models and machine code. VeriPhy reduces CPS safety to the faithfulness of the physical environment, which is checked at runtime by synthesized, verified monitors. We use three provers in this effort: KeYmaera X, HOL4, and Isabelle/HOL. To minimize the trusted base, we cross-verify KeYmaeraX in Isabelle/HOL. We evaluate the resulting controller and monitors on commodity robotics hardware.
{"title":"VeriPhy: verified controller executables from verified cyber-physical system models","authors":"Brandon Bohrer, Yong Kiam Tan, Stefan Mitsch, Magnus O. Myreen, André Platzer","doi":"10.1145/3192366.3192406","DOIUrl":"https://doi.org/10.1145/3192366.3192406","url":null,"abstract":"We present VeriPhy, a verified pipeline which automatically transforms verified high-level models of safety-critical cyber-physical systems (CPSs) in differential dynamic logic (dL) to verified controller executables. VeriPhy proves that all safety results are preserved end-to-end as it bridges abstraction gaps, including: i) the gap between mathematical reals in physical models and machine arithmetic in the implementation, ii) the gap between real physics and its differential-equation models, and iii) the gap between nondeterministic controller models and machine code. VeriPhy reduces CPS safety to the faithfulness of the physical environment, which is checked at runtime by synthesized, verified monitors. We use three provers in this effort: KeYmaera X, HOL4, and Isabelle/HOL. To minimize the trusted base, we cross-verify KeYmaeraX in Isabelle/HOL. We evaluate the resulting controller and monitors on commodity robotics hardware.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76874127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present Ryū, a new routine to convert binary floating point numbers to their decimal representations using only fixed-size integer operations, and prove its correctness. Ryū is simpler and approximately three times faster than the previously fastest implementation.
{"title":"Ryū: fast float-to-string conversion","authors":"Ulf Adams","doi":"10.1145/3192366.3192369","DOIUrl":"https://doi.org/10.1145/3192366.3192369","url":null,"abstract":"We present Ryū, a new routine to convert binary floating point numbers to their decimal representations using only fixed-size integer operations, and prove its correctness. Ryū is simpler and approximately three times faster than the previously fastest implementation.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80034005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An immutable multi-map is a many-to-many map data structure with expected fast insert and lookup operations. This data structure is used for applications processing graphs or many-to-many relations as applied in compilers, runtimes of programming languages, or in static analysis of object-oriented systems. Collection data structures are assumed to carefully balance execution time of operations with memory consumption characteristics and need to scale gracefully from a few elements to multiple gigabytes at least. When processing larger in-memory data sets the overhead of the data structure encoding itself becomes a memory usage bottleneck, dominating the overall performance. In this paper we propose AXIOM, a novel hash-trie data structure that allows for a highly efficient and type-safe multi-map encoding by distinguishing inlined values of singleton sets from nested sets of multi-mappings. AXIOM strictly generalizes over previous hash-trie data structures by supporting the processing of fine-grained type-heterogeneous content on the implementation level (while API and language support for type-heterogeneity are not scope of this paper). We detail the design and optimizations of AXIOM and further compare it against state-of-the-art immutable maps and multi-maps in Java, Scala and Clojure. We isolate key differences using microbenchmarks and validate the resulting conclusions on a case study in static analysis. AXIOM reduces the key-value storage overhead by 1.87x; with specializing and inlining across collection boundaries it improves by 5.1x.
{"title":"To-many or to-one? all-in-one! efficient purely functional multi-maps with type-heterogeneous hash-tries","authors":"M. Steindorfer, J. Vinju","doi":"10.1145/3192366.3192420","DOIUrl":"https://doi.org/10.1145/3192366.3192420","url":null,"abstract":"An immutable multi-map is a many-to-many map data structure with expected fast insert and lookup operations. This data structure is used for applications processing graphs or many-to-many relations as applied in compilers, runtimes of programming languages, or in static analysis of object-oriented systems. Collection data structures are assumed to carefully balance execution time of operations with memory consumption characteristics and need to scale gracefully from a few elements to multiple gigabytes at least. When processing larger in-memory data sets the overhead of the data structure encoding itself becomes a memory usage bottleneck, dominating the overall performance. In this paper we propose AXIOM, a novel hash-trie data structure that allows for a highly efficient and type-safe multi-map encoding by distinguishing inlined values of singleton sets from nested sets of multi-mappings. AXIOM strictly generalizes over previous hash-trie data structures by supporting the processing of fine-grained type-heterogeneous content on the implementation level (while API and language support for type-heterogeneity are not scope of this paper). We detail the design and optimizations of AXIOM and further compare it against state-of-the-art immutable maps and multi-maps in Java, Scala and Clojure. We isolate key differences using microbenchmarks and validate the resulting conclusions on a case study in static analysis. AXIOM reduces the key-value storage overhead by 1.87x; with specializing and inlining across collection boundaries it improves by 5.1x.","PeriodicalId":20583,"journal":{"name":"Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81800500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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