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The Computational Power and Complexity of Constraint Handling Rules
- In Second Workshop on Constraint Handling Rules, at ICLP05
, 2005
"... Constraint Handling Rules (CHR) is a high-level rule-based programming language which is increasingly used for general purposes. We introduce the CHR machine, a model of computation based on the operational semantics of CHR. Its computational power and time complexity properties are compared to thos ..."
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Cited by 52 (21 self)
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Constraint Handling Rules (CHR) is a high-level rule-based programming language which is increasingly used for general purposes. We introduce the CHR machine, a model of computation based on the operational semantics of CHR. Its computational power and time complexity properties are compared to those of the well-understood Turing machine and Random Access Memory machine. This allows us to prove the interesting result that every algorithm can be implemented in CHR with the best known time and space complexity. We also investigate the practical relevance of this result and the constant factors involved. Finally we expand the scope of the discussion to other (declarative) programming languages.
Optimal Union-Find in Constraint Handling Rules
- UNDER CONSIDERATION FOR PUBLICATION IN THEORY AND PRACTICE OF LOGIC PROGRAMMING
, 2005
"... Constraint Handling Rules (CHR) is a committed-choice rule-based language that was originally intended for writing constraint solvers. In this paper we show that it is also possible to write the classic union-find algorithm and variants in CHR. The programs neither compromise in declarativeness nor ..."
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Cited by 36 (24 self)
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Constraint Handling Rules (CHR) is a committed-choice rule-based language that was originally intended for writing constraint solvers. In this paper we show that it is also possible to write the classic union-find algorithm and variants in CHR. The programs neither compromise in declarativeness nor efficiency. We study the time complexity of our programs: they match the almost-linear complexity of the best known imperative implementations. This fact is illustrated with experimental results.
Abstract Interpretation for Constraint Handling Rules
- In Proceedings of the 7th Intl. Conference on Principles and Practice of Declarative Programming (PPDP’05
, 2005
"... Program analysis is essential for the optimized compilation of Constraint Handling Rules (CHRs) as well as the inference of behavioral properties such as confluence and termination. Up to now all program analyses for CHRs have been developed in an ad hoc fashion. In this work we bring the general pr ..."
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Cited by 27 (17 self)
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Program analysis is essential for the optimized compilation of Constraint Handling Rules (CHRs) as well as the inference of behavioral properties such as confluence and termination. Up to now all program analyses for CHRs have been developed in an ad hoc fashion. In this work we bring the general program analysis methodology of abstract interpretation to CHRs: we formulate an abstract interpretation framework over the call-based operational semantics of CHRs. The abstract interpretation framework is non-obvious since it needs to handle the highly non-deterministic execution of CHRs. The use of the framework is illustrated with two instantiations: the CHR-specific late storage analysis and the more generally known groundness analysis. In addition, we discuss optimizations based on these analyses and present experimental results. Categories and Subject Descriptors D.3.2 [Programming Languages]: Language Classifications—Constraint and logic languages; F.3.2 [Logics and
K.U.Leuven JCHR: a user-friendly, flexible and efficient CHR system for Java
- IN PROC. 2ND WORKSHOP ON CONSTRAINT HANDLING RULES (CHR’05
, 2005
"... A new integration of Constraint Handling Rules (CHR) and Java is presented: the K.U.Leuven JCHR system. It was designed with three aims in mind: user-friendliness, flexibility and efficiency. User-friendliness is achieved by providing a high-level syntax that feels familiar to both Java programmers ..."
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Cited by 23 (13 self)
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A new integration of Constraint Handling Rules (CHR) and Java is presented: the K.U.Leuven JCHR system. It was designed with three aims in mind: user-friendliness, flexibility and efficiency. User-friendliness is achieved by providing a high-level syntax that feels familiar to both Java programmers and users of other CHR embeddings, and by full compliance to the refined operational semantics. Flexibility is the result of a well thought-out design, allowing e.g. an easy integration of built-in constraint solvers and variable types. Efficiency is achieved through an optimized compilation to Java and the use of a very efficient constraint store. The design of the K.U.Leuven JCHR system is presented, its implementation discussed and its performance is compared with other CHR systems embedded in Java and Prolog.
Automatic Implication Checking for CHR Constraints
, 2005
"... Constraint Handling Rules (CHRs) are a high-level rule-based programming language commonly used to define constraint solvers. We present a method for automatic implication checking between constraints of CHR solvers. Supporting implication is important for implementing extensible solvers and reifica ..."
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Cited by 16 (13 self)
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Constraint Handling Rules (CHRs) are a high-level rule-based programming language commonly used to define constraint solvers. We present a method for automatic implication checking between constraints of CHR solvers. Supporting implication is important for implementing extensible solvers and reification, and for building hierarchical CHR constraint solvers. Our method does not copy the entire constraint store, but performs the check in place using a trailing mechanism. The necessary code enhancements can be done by automatic program transformation based on the rules of the solver. We extend our method to work for hierarchically organized modular CHR solvers. We show the soundness of our method and its completeness for a restricted class of canonical solver as well as for specific existing non-canonical CHR solvers. We evaluate our trailing method experimentally by comparing with the copy approach: runtime is almost halved.
As time goes by: Constraint handling rules -- A survey of CHR research between 1998 and 2007
, 2009
"... Constraint Handling Rules (CHR) is a high-level programming language based on multiheaded multiset rewrite rules. Originally designed for writing user-defined constraint solvers, it is now recognized as an elegant general purpose language. CHR-related research has surged during the decade following ..."
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Cited by 16 (11 self)
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Constraint Handling Rules (CHR) is a high-level programming language based on multiheaded multiset rewrite rules. Originally designed for writing user-defined constraint solvers, it is now recognized as an elegant general purpose language. CHR-related research has surged during the decade following the previous survey by Frühwirth (1998). Covering more than 180 publications, this new survey provides an overview of recent results in a wide range of research areas, from semantics and analysis to systems, extensions and applications.
Compiling Constraint Handling Rules for Efficient Tabled Evaluation
- In 9th International Symposium on Practical Aspects of Declarative Languages (PADL
, 2007
"... Abstract. Tabled resolution, which alleviates some of Prolog’s termination problems, makes it possible to create practical applications from high-level declarative specifications. Constraint Handling Rules (CHR) is an elegant framework for implementing constraint solvers from high-level specificatio ..."
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Cited by 15 (3 self)
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Abstract. Tabled resolution, which alleviates some of Prolog’s termination problems, makes it possible to create practical applications from high-level declarative specifications. Constraint Handling Rules (CHR) is an elegant framework for implementing constraint solvers from high-level specifications, and is available in many Prolog systems. However, applications combining the power of these two declarative paradigms have been impractical since traditional CHR implementations interact poorly with tabling. In this paper we present a new (set-based) semantics for CHR which enables efficient integration with tabling. The new semantics coincides with the traditional (multi-set-based) semantics for a large class of CHR programs. We describe CHRd, an implementation based on the new semantics. CHRd uses a distributed constraint store that can be directly represented in tables. Although motivated by tabling, CHRd works well also on non-tabled platforms. We present experimental results which show that, relative to traditional implementations, CHRd performs significantly better on tabled programs, and yet shows comparable results on non-tabled benchmarks. 1
CCHR: the fastest CHR implementation
- in C,” in Proc. 4th Workshop on Constraint Handling Rules (CHR’07), 2007
"... Abstract. CHR is usually compiled to high-level languages (like Prolog) that make it hard or impossible to express low-level optimizations. This is a pity, because it confines CHR to be a prototyping language only, with an unacceptable performance for production quality software. This paper presents ..."
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Cited by 10 (4 self)
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Abstract. CHR is usually compiled to high-level languages (like Prolog) that make it hard or impossible to express low-level optimizations. This is a pity, because it confines CHR to be a prototyping language only, with an unacceptable performance for production quality software. This paper presents CCHR, a CHR system embedded in the C programming language, that compiles to low-level C code which is highly suitable for fine-grained performance improvements. In this way CCHR program performance comes close to matching that of native C, and easily outperforms other CHR implementations. 1
