The authors' ATR programming formalism is a version of call-by-value PCF under a complexity-theoretically motivated type system. ATR programs run in type-2 polynomial-time and all standard type-2 basic feasible fu...
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The authors' ATR programming formalism is a version of call-by-value PCF under a complexity-theoretically motivated type system. ATR programs run in type-2 polynomial-time and all standard type-2 basic feasible functionals are ATR-definable (ATR types are confined to levels 0, 1, and 2). A limitation of the original version of ATR is that the only directly expressible recursions are tail-recursions. Here we extend ATR so that a broad range of affine recursions are directly expressible. In particular, the revised ATR can fairly naturally express the classic insertion-and selection-sort algorithms, thus overcoming a sticking point of most prior implicit-complexity-based formalisms. The paper's main work is in refining the original time-complexity semantics for ATR to show that these new recursion schemes do not lead out of the realm of feasibility.
The earlier paper "Introduction to clarithmetic I" constructed an axiomatic system of arithmetic based on computability logic, and proved its soundness and extensional completeness with respect to polynomial...
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The earlier paper "Introduction to clarithmetic I" constructed an axiomatic system of arithmetic based on computability logic, and proved its soundness and extensional completeness with respect to polynomial time computability. The present paper elaborates three additional sound and complete systems in the same style and sense: one for polynomial space computability, one for elementary recursive time (and/or space) computability, and one for primitive recursive time (and/or space) computability (C) 2016 Elsevier Inc. All rights reserved.
"Clarithmetic" is a generic name for formal number theories similar to Peano arithmetic, but based on computability logic instead of the more traditional classical or intuitionistic logics. Formulas of clari...
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"Clarithmetic" is a generic name for formal number theories similar to Peano arithmetic, but based on computability logic instead of the more traditional classical or intuitionistic logics. Formulas of clarithmetical theories represent interactive computational problems, and their "truth" is understood as existence of an algorithmic solution. Imposing various complexity constraints on such solutions yields various versions of clarithmetic. The present paper introduces a system of clarithmetic for polynomial time computability, which is shown to be sound and complete. Sound in the sense that every theorem T of the system represents an interactive number-theoretic computational problem with a polynomial time solution and, furthermore, such a solution can be efficiently extracted from a proof of T. And complete in the sense that every interactive number-theoretic problem with a polynomial time solution is represented by some theorem T of the system. The paper is written in a semitutorial style and targets readers with no prior familiarity with computability logic. (C) 2011 Elsevier Inc. All rights reserved.
Polynomial interpretations and their generalizations like quasi-interpretations have been used in the setting of first-order functional languages to design criteria ensuring statically some complexity bounds on progra...
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Polynomial interpretations and their generalizations like quasi-interpretations have been used in the setting of first-order functional languages to design criteria ensuring statically some complexity bounds on programs[10]. This fits in the area of implicit computational complexity, which aims at giving machine-free characterizations of complexity classes. In this paper, we extend this approach to the higher-order setting. For that we consider simply-typed term rewriting systems[35], we define higher-order polynomial interpretations for them, and we give a criterion ensuring that a program can be executed in polynomial time. In order to obtain a criterion flexible enough to validate interesting programs using higher-order primitives, we introduce a notion of polynomial quasi-interpretations, coupled with a simple termination criterion based on linear types and path-like orders. (C) 2016 Elsevier Inc. All rights reserved.
We give recursion-theoretic characterizations of the counting class #P, the class of those functions which count the number of accepting computations of non-deterministic Turing machines working in polynomial time. Mo...
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We give recursion-theoretic characterizations of the counting class #P, the class of those functions which count the number of accepting computations of non-deterministic Turing machines working in polynomial time. Moreover, we characterize in a recursion-theoretic manner all the levels {#P-k}(k is an element of N) of the counting hierarchy of functions FCH, which result from allowing queries to functions of the previous level, and FCH itself as a whole. This is done in the style of Bellantoni and Cook's safe recursion, and it places #P in the context of implicit computational complexity. Namely, it relates #P with the implicit characterizations of FPTIME (Bellantoni and Cook, Comput Complex 2:97-110,1992) and FPSPACE (Oitavem, Math Log Q 54(3):317-323, 2008), by exploiting the features of the tree-recursion scheme of FPSPACE.
Starting from Girard's seminal paper on light linear logic (LLL), a number of works investigated systems derived from linear logic to capture polynomial time computation within the computation-as-cut-elimination p...
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Starting from Girard's seminal paper on light linear logic (LLL), a number of works investigated systems derived from linear logic to capture polynomial time computation within the computation-as-cut-elimination paradigm. The original syntax of LLL is too complicated, mainly because one has to deal with sequents which do not just consist of formulas but also of 'blocks' of formulas. We circumvent the complications of 'blocks' by introducing a new modality del which is exclusively in charge of 'additive blocks'. One of the most interesting features of this purely multiplicative del is the possibility of the second-order encodings of additive connectives. The resulting system (with the traditional syntax), called Easy-LLL, is still powerful to represent any deterministic polynomial time computations in purely logical terms. Unlike the original LLL, Easy-LLL admits polynomial time strong normalization together with the Church-Rosser property, namely, cut elimination terminates in a unique way in polytime by any choice of cut reduction strategies. (c) 2011 Elsevier B.V. All rights reserved.
A language is defined by closure under safe iteration and under a new form of safe diagonalization that, unlike other forms of diagonalization used in literature to define sub-recursive hierarchies, is constructive an...
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A language is defined by closure under safe iteration and under a new form of safe diagonalization that, unlike other forms of diagonalization used in literature to define sub-recursive hierarchies, is constructive and decidable. By counting the nesting levels of these schemes, an ordinal is assigned to each program. This yields a hierarchy T-alpha (alpha < omega(omega)) that singles-out the complexity classes DTIMEF(n(cnd+e)) for all c, d, e >= 0. (c) 2005 Elsevier B.V. All rights reserved.
We combine dependent types with linear type systems that soundly and completely capture polynomial time computation. We explore two systems for capturing polynomial time: one system that disallows construction of iter...
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We combine dependent types with linear type systems that soundly and completely capture polynomial time computation. We explore two systems for capturing polynomial time: one system that disallows construction of iterable data, and one, based on the LFPL system of Martin Hofmann, that controls construction via a payment method. Both of these are extended to full dependent types via Quantitative Type Theory, allowing for arbitrary computation in types alongside guaranteed polynomial time computation in terms. We prove the soundness of the systems using a realisability technique due to Dal Lago and Hofmann. Our long-term goal is to combine the extensional reasoning of type theory with intensional reasoning about the resources intrinsically consumed by programs. This paper is a step along this path, which we hope will lead both to practical systems for reasoning about programs' resource usage, and to theoretical use as a form of synthetic computationalcomplexity theory.
We describe some results inspired to Lafont's Soft Linear Logic (SLL) which is a subsystem of second-order linear logic with restricted rules for exponentials, correct and complete for polynomial time computations...
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We describe some results inspired to Lafont's Soft Linear Logic (SLL) which is a subsystem of second-order linear logic with restricted rules for exponentials, correct and complete for polynomial time computations. SLL is the basis for the design of type assignment systems for lambda-calculus, characterizing the complexity classes PTIME, PSPACE and NPTIME. PTIME is characterized by a type assignments system where types are a proper subset of SLL formulae. The characterization consists in the fact that a well typed term can be reduced to normal form by a number of beta-reductions polynomial in its lenght, and moreover all polynomial time functions can be computed by well typed terms. PSPACE is characterized by a type assignment system obtained from the previous one, by extending the set of types by a type for booleans, and the lambda-calculus by two boolean constants and a conditional constructor. The system assigns types to terms in such a way that the evaluation of programs (closed terms of type boolean) can be performed carefully in polynomial space. Moreover all polynomial space decision problems can be computed by terms typable in this system. In order to characterize NPTIME we extend the lambda-calculus by a nondeterministic choice operator, and the system by a rule for dealing with this new term constructor.
This paper is concerned with implicit computational complexity of the exptime computable functions. Modifying the lexicographic path order, we introduce a path order EPO. It is shown that a termination proof for a ter...
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This paper is concerned with implicit computational complexity of the exptime computable functions. Modifying the lexicographic path order, we introduce a path order EPO. It is shown that a termination proof for a term rewriting system via EPO implies an exponential bound on the lengths of derivations. The path order EPO is designed so that every exptime function is representable as a term rewrite system compatible with EPO. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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