Although laziness enables beautiful code, it comes with non-trivial performance costs. The ghc compiler for Haskell has optimizations to reduce those costs, but the optimizations are not sufficient. As a result, Haskell also provides a variety of strictness annotations so that users can indicate program points where an expression should be evaluated eagerly. Skillful use of those annotations is a black art, known only to expert Haskell programmers. In this paper, we introduce AUTOBAHN, a tool that uses genetic algorithms to automatically infer strictness annotations that improve program performance on representative inputs. Users examine the suggested annotations for soundness and can instruct AUTOBAHN to automatically produce modified sources. Experiments on 60 programs from the NoFib benchmark suite show that AUTOBAHN can infer annotation sets that improve runtime performance by a geometric mean of 8.5%. Case studies show AUTOBAHN can reduce the live size of a GC simulator by 99% and infer application-specific annotations for Aeson library code. A 10-fold cross-validation study shows the AUTOBAHN -optimized GC simulator generally outperforms a version optimized by an expert.
{"title":"Autobahn: using genetic algorithms to infer strictness annotations","authors":"Y. Wang, Diogenes Nunez, Kathleen Fisher","doi":"10.1145/2976002.2976009","DOIUrl":"https://doi.org/10.1145/2976002.2976009","url":null,"abstract":"Although laziness enables beautiful code, it comes with non-trivial performance costs. The ghc compiler for Haskell has optimizations to reduce those costs, but the optimizations are not sufficient. As a result, Haskell also provides a variety of strictness annotations so that users can indicate program points where an expression should be evaluated eagerly. Skillful use of those annotations is a black art, known only to expert Haskell programmers. In this paper, we introduce AUTOBAHN, a tool that uses genetic algorithms to automatically infer strictness annotations that improve program performance on representative inputs. Users examine the suggested annotations for soundness and can instruct AUTOBAHN to automatically produce modified sources. Experiments on 60 programs from the NoFib benchmark suite show that AUTOBAHN can infer annotation sets that improve runtime performance by a geometric mean of 8.5%. Case studies show AUTOBAHN can reduce the live size of a GC simulator by 99% and infer application-specific annotations for Aeson library code. A 10-fold cross-validation study shows the AUTOBAHN -optimized GC simulator generally outperforms a version optimized by an expert.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85298620","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}
Monads have taken the world by storm, and are supported by do-notation (at least in Haskell). Programmers are increasingly waking up to the usefulness and ubiquity of Applicatives, but they have so far been hampered by the absence of supporting notation. In this paper we show how to re-use the very same do-notation to work for Applicatives as well, providing efficiency benefits for some types that are both Monad and Applicative, and syntactic convenience for those that are merely Applicative. The result is fully implemented as an optional extension in GHC, and is in use at Facebook to make it easy to write highly-parallel queries in a distributed system.
{"title":"Desugaring Haskell's do-notation into applicative operations","authors":"S. Marlow, S. Jones, Edward Kmett, A. Mokhov","doi":"10.1145/2976002.2976007","DOIUrl":"https://doi.org/10.1145/2976002.2976007","url":null,"abstract":"Monads have taken the world by storm, and are supported by do-notation (at least in Haskell). Programmers are increasingly waking up to the usefulness and ubiquity of Applicatives, but they have so far been hampered by the absence of supporting notation. In this paper we show how to re-use the very same do-notation to work for Applicatives as well, providing efficiency benefits for some types that are both Monad and Applicative, and syntactic convenience for those that are merely Applicative. The result is fully implemented as an optional extension in GHC, and is in use at Facebook to make it easy to write highly-parallel queries in a distributed system.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85337662","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}
This paper presents FitSpec, a tool providing automated assistance in the task of refining sets of test properties for Haskell functions. FitSpec tests mutant variations of functions under test against a given property set, recording any surviving mutants that pass all tests. The number of surviving mutants and any smallest survivor are presented to the user. A surviving mutant indicates incompleteness of the property set, prompting the user to amend a property or to add a new one, making the property set stronger. Based on the same test results, FitSpec also provides conjectures in the form of equivalences and implications between property subsets. These conjectures help the user to identify minimal core subsets of properties and so to reduce the cost of future property-based testing.
{"title":"FitSpec: refining property sets for functional testing","authors":"Rudy Matela, C. Runciman","doi":"10.1145/2976002.2976003","DOIUrl":"https://doi.org/10.1145/2976002.2976003","url":null,"abstract":"This paper presents FitSpec, a tool providing automated assistance in the task of refining sets of test properties for Haskell functions. FitSpec tests mutant variations of functions under test against a given property set, recording any surviving mutants that pass all tests. The number of surviving mutants and any smallest survivor are presented to the user. A surviving mutant indicates incompleteness of the property set, prompting the user to amend a property or to add a new one, making the property set stronger. Based on the same test results, FitSpec also provides conjectures in the form of equivalences and implications between property subsets. These conjectures help the user to identify minimal core subsets of properties and so to reduce the cost of future property-based testing.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79424981","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}
Remote procedure calls are computationally expensive, because network round-trips take several orders of magnitude longer than local interactions. One common technique for amortizing this cost is to batch together multiple independent requests into one compound request. Batching requests amounts to serializing the abstract syntax tree of a small program, in order to transmit it and run it remotely. The standard representation for abstract syntax is to use free monads; we show that free applicative functors are actually a better choice of representation for this scenario.
{"title":"Free delivery (functional pearl)","authors":"J. Gibbons","doi":"10.1145/2976002.2976005","DOIUrl":"https://doi.org/10.1145/2976002.2976005","url":null,"abstract":"Remote procedure calls are computationally expensive, because network round-trips take several orders of magnitude longer than local interactions. One common technique for amortizing this cost is to batch together multiple independent requests into one compound request. Batching requests amounts to serializing the abstract syntax tree of a small program, in order to transmit it and run it remotely. The standard representation for abstract syntax is to use free monads; we show that free applicative functors are actually a better choice of representation for this scenario.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79187870","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}
Causal commutative arrows (CCA) extend arrows with additional constructs and laws that make them suitable for modelling domains such as functional reactive programming, differential equations and synchronous dataflow. Earlier work has revealed that a syntactic transformation of CCA computations into normal form can result in significant performance improvements, sometimes increasing the speed of programs by orders of magnitude. In this work we reformulate the normalization as a type class instance and derive optimized observation functions via a specialization to stream transformers to demonstrate that the same dramatic improvements can be achieved without leaving the language.
{"title":"Causal commutative arrows revisited","authors":"J. Yallop, Hai Liu","doi":"10.1145/2976002.2976019","DOIUrl":"https://doi.org/10.1145/2976002.2976019","url":null,"abstract":"Causal commutative arrows (CCA) extend arrows with additional constructs and laws that make them suitable for modelling domains such as functional reactive programming, differential equations and synchronous dataflow. Earlier work has revealed that a syntactic transformation of CCA computations into normal form can result in significant performance improvements, sometimes increasing the speed of programs by orders of magnitude. In this work we reformulate the normalization as a type class instance and derive optimized observation functions via a specialization to stream transformers to demonstrate that the same dramatic improvements can be achieved without leaving the language.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87744223","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}
Matthew Pickering, Gergo Érdi, S. Jones, R. Eisenberg
Pattern matching has proven to be a convenient, expressive way of inspecting data. Yet this language feature, in its traditional form, is limited: patterns must be data constructors of concrete data types. No computation or abstraction is allowed. The data type in question must be concrete, with no ability to enforce any invariants. Any change in this data type requires all clients to update their code. This paper introduces pattern synonyms, which allow programmers to abstract over patterns, painting over all the shortcomings listed above. Pattern synonyms are assigned types, enabling a compiler to check the validity of a synonym independent of its definition. These types are intricate; detailing how to assign a type to a pattern synonym is a key contribution of this work. We have implemented pattern synonyms in the Glasgow Haskell Compiler, where they have enjoyed immediate popularity, but we believe this feature could easily be exported to other languages that support pattern matching.
{"title":"Pattern synonyms","authors":"Matthew Pickering, Gergo Érdi, S. Jones, R. Eisenberg","doi":"10.1145/2976002.2976013","DOIUrl":"https://doi.org/10.1145/2976002.2976013","url":null,"abstract":"Pattern matching has proven to be a convenient, expressive way of inspecting data. Yet this language feature, in its traditional form, is limited: patterns must be data constructors of concrete data types. No computation or abstraction is allowed. The data type in question must be concrete, with no ability to enforce any invariants. Any change in this data type requires all clients to update their code. This paper introduces pattern synonyms, which allow programmers to abstract over patterns, painting over all the shortcomings listed above. Pattern synonyms are assigned types, enabling a compiler to check the validity of a synonym independent of its definition. These types are intricate; detailing how to assign a type to a pattern synonym is a key contribution of this work. We have implemented pattern synonyms in the Glasgow Haskell Compiler, where they have enjoyed immediate popularity, but we believe this feature could easily be exported to other languages that support pattern matching.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83022425","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}
Most build systems start small and simple, but over time grow into hairy monsters that few dare to touch. As we demonstrate in this paper, there are a few issues that cause build systems major scalability challenges, and many pervasively used build systems (e.g. Make) do not scale well. This paper presents a solution to the challenges we identify. We use functional programming to design abstractions for build systems, and implement them on top of the Shake library, which allows us to describe build rules and dependencies. To substantiate our claims, we engineer a new build system for the Glasgow Haskell Compiler. The result is more scalable, faster, and spectacularly more maintainable than its Make-based predecessor.
{"title":"Non-recursive make considered harmful: build systems at scale","authors":"A. Mokhov, Neil Mitchell, S. Jones, S. Marlow","doi":"10.1145/2976002.2976011","DOIUrl":"https://doi.org/10.1145/2976002.2976011","url":null,"abstract":"Most build systems start small and simple, but over time grow into hairy monsters that few dare to touch. As we demonstrate in this paper, there are a few issues that cause build systems major scalability challenges, and many pervasively used build systems (e.g. Make) do not scale well. This paper presents a solution to the challenges we identify. We use functional programming to design abstractions for build systems, and implement them on top of the Shake library, which allows us to describe build rules and dependencies. To substantiate our claims, we engineer a new build system for the Glasgow Haskell Compiler. The result is more scalable, faster, and spectacularly more maintainable than its Make-based predecessor.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77431334","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}
Functional Reactive Programming (FRP) has come to mean many things. Yet, scratch the surface of the multitude of realisations, and there is great commonality between them. This paper investigates this commonality, turning it into a mathematically coherent and practical FRP realisation that allows us to express the functionality of many existing FRP systems and beyond by providing a minimal FRP core parameterised on a monad. We give proofs for our theoretical claims and we have verified the practical side by benchmarking a set of existing, non-trivial Yampa applications running on top of our new system with very good results.
{"title":"Functional reactive programming, refactored","authors":"Ivan Perez, Manuel Bärenz, H. Nilsson","doi":"10.1145/2976002.2976010","DOIUrl":"https://doi.org/10.1145/2976002.2976010","url":null,"abstract":"Functional Reactive Programming (FRP) has come to mean many things. Yet, scratch the surface of the multitude of realisations, and there is great commonality between them. This paper investigates this commonality, turning it into a mathematically coherent and practical FRP realisation that allows us to express the functionality of many existing FRP systems and beyond by providing a minimal FRP core parameterised on a monad. We give proofs for our theoretical claims and we have verified the practical side by benchmarking a set of existing, non-trivial Yampa applications running on top of our new system with very good results.","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83179402","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}
{"title":"Proceedings of the 9th International Symposium on Haskell","authors":"","doi":"10.1145/2976002","DOIUrl":"https://doi.org/10.1145/2976002","url":null,"abstract":"","PeriodicalId":20669,"journal":{"name":"Proceedings of the 9th International Symposium on Haskell","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91480321","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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