Results 1  10
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16
Learning Recursive Functions from Approximations
, 1995
"... Investigated is algorithmic learning, in the limit, of correct programs for recursive functions f from both input/output examples of f and several interesting varieties of approximate additional (algorithmic) information about f . Specifically considered, as such approximate additional informatio ..."
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Cited by 17 (7 self)
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Investigated is algorithmic learning, in the limit, of correct programs for recursive functions f from both input/output examples of f and several interesting varieties of approximate additional (algorithmic) information about f . Specifically considered, as such approximate additional information about f , are Rose's frequency computations for f and several natural generalizations from the literature, each generalization involving programs for restricted trees of recursive functions which have f as a branch. Considered as the types of trees are those with bounded variation, bounded width, and bounded rank. For the case of learning final correct programs for recursive functions, EX learning, where the additional information involves frequency computations, an insightful and interestingly complex combinatorial characterization of learning power is presented as a function of the frequency parameters. For EX learning (as well as for BClearning, where a final sequence of cor...
Effective Hausdorff dimension
 In Logic Colloquium ’01
, 2005
"... ABSTRACT. We continue the study of effective Hausdorff dimension as it was initiated by LUTZ. Whereas he uses a generalization of martingales on the Cantor space to introduce this notion we give a characterization in terms of effective sdimensional Hausdorff measures, similar to the effectivization ..."
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Cited by 5 (2 self)
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ABSTRACT. We continue the study of effective Hausdorff dimension as it was initiated by LUTZ. Whereas he uses a generalization of martingales on the Cantor space to introduce this notion we give a characterization in terms of effective sdimensional Hausdorff measures, similar to the effectivization of Lebesgue measure by MARTINLÖF. It turns out that effective Hausdorff dimension allows to classify sequences according to their ‘degree ’ of algorithmic randomness, i.e., their algorithmic density of information. Earlier the works of STAIGER and RYABKO showed a deep connection between Kolmogorov complexity and Hausdorff dimension. We further develop this relationship and use it to give effective versions of some important properties of (classical) Hausdorff dimension. Finally, we determine the effective dimension of some objects arising in the context of computability theory, such as degrees and spans. 1.
The Communication Complexity of Enumeration, Elimination, and Selection
"... y1) f(xk , yk )) communicating as few bits as possible. The Direct Sum Conjecture (henceforth DSC) of Karchmer, Raz, and Wigderson, states that the obvious way to compute it (computing f(x1 , y1 ), then f(x2 , y2 ), etc.) is, roughly speaking, the best. This conjecture arose in the study of cir ..."
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Cited by 4 (1 self)
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y1) f(xk , yk )) communicating as few bits as possible. The Direct Sum Conjecture (henceforth DSC) of Karchmer, Raz, and Wigderson, states that the obvious way to compute it (computing f(x1 , y1 ), then f(x2 , y2 ), etc.) is, roughly speaking, the best. This conjecture arose in the study of circuits since a variant of it implies NC 1 #= NC 2 . We consider two related problems. Enumeration: Alice and Bob output e # 2 k  1 elements of {0, 1} k , one of which is f(x1 , y1) f(xk , yk ). Elimination: Alice and Bob output # b such that # b #= f(x1 , y1 ) f(xk , yk ). Selection: (k = 2) Al
On the Structures Inside TruthTable Degrees
 Forschungsberichte Mathematische Logik 29 / 1997, Mathematisches Institut, Universitat
, 1997
"... . The following theorems on the structure inside nonrecursive truthtable degrees are established: Degtev's result that the number of bounded truthtable degrees inside a truthtable degree is at least two is improved by showing that this number is infinite. There are even infinite chains and ..."
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Cited by 4 (2 self)
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. The following theorems on the structure inside nonrecursive truthtable degrees are established: Degtev's result that the number of bounded truthtable degrees inside a truthtable degree is at least two is improved by showing that this number is infinite. There are even infinite chains and antichains of bounded truthtable degrees inside the truthtable degrees which implies an affirmative answer to a question of Jockusch whether every truthtable degree contains an infinite antichain of manyone degrees. Some but not all truthtable degrees have a least bounded truthtable degree. The technique to construct such a degree is used to solve an open problem of Beigel, Gasarch and Owings: there are Turing degrees (constructed as hyperimmunefree truthtable degrees) which consist only of 2subjective sets and do therefore not contain any objective set. Furthermore a truthtable degree consisting of three positive degrees is constructed where one positive degree consists of enum...
On the Reducibility of Sets Inside NP to Sets with Low Information Content
, 2002
"... We study whether sets inside NP can be reduced to sets with low information content but possibly still high computational complexity. Examples of sets with low information content are tally sets, sparse sets, Pselective sets and membership comparable sets. For the graph automorphism... ..."
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Cited by 2 (1 self)
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We study whether sets inside NP can be reduced to sets with low information content but possibly still high computational complexity. Examples of sets with low information content are tally sets, sparse sets, Pselective sets and membership comparable sets. For the graph automorphism...
A Structural Property of Regular Frequency Computations
 Theoretical Comput. Sci
, 2000
"... . The notion of an (m; n){computation was already introduced in 1960 by Rose and further investigated by Trakhtenbrot in 1963. It has been extended to nite automata by Kinber in 1976 and he has shown an analogue of Trakhtenbrot's result: The class of languages (m; n) recognizable by determ ..."
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Cited by 2 (1 self)
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. The notion of an (m; n){computation was already introduced in 1960 by Rose and further investigated by Trakhtenbrot in 1963. It has been extended to nite automata by Kinber in 1976 and he has shown an analogue of Trakhtenbrot's result: The class of languages (m; n) recognizable by deterministic nite automata is equal to the class of regular languages if and only if 2m > n. Furthermore, for a unary alphabet, the class of (m; n)recognizable languages coincides with the class of regular languages for all m and n. In this paper, we will present the rst structural property of (m; n) recognizable languages which is valid for all 1 m n and for all alphabets. Kinber's result for unary alphabets becomes a corollary. This property is also used to show that certain nonunary languages are not (m; n)regular and that the class of all (m; n)recognizable languages is not closed under the reversal operation. However, this class forms a Boolean algebra. 1 Introduction The ...
Combining SelfReducibility and Partial Information Algorithms
"... Abstract. A partial information algorithm for a language A computes, for some fixed m, for input words x1,..., xm a set of bitstrings containing χA(x1,..., xm). E.g., pselective, approximable, and easily countable languages are defined by the existence of polynomialtime partial information algorit ..."
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Abstract. A partial information algorithm for a language A computes, for some fixed m, for input words x1,..., xm a set of bitstrings containing χA(x1,..., xm). E.g., pselective, approximable, and easily countable languages are defined by the existence of polynomialtime partial information algorithms of specific type. Selfreducible languages, for different types of selfreductions, form subclasses of PSPACE. For a selfreducible language A, the existence of a partial information algorithm sometimes helps to place A into some subclass of PSPACE. The most prominent known result in this respect is: Pselective languages which are selfreducible are in P [9]. Closely related is the fact that the existence of a partial information algorithm for A simplifies the type of reductions or selfreductions to A. The most prominent known result in this respect is: Turing reductions to easily countable languages simplify to truthtable reductions [8]. We prove new results of this type. We show: 1. Selfreducible languages which are easily 2countable are in P. This partially confirms a conjecture of [8]. 2. Selfreducible languages which are (2m − 1, m)verbose are truthtable selfreducible. This generalizes the result of [9] for pselective languages, which are (m + 1, m)verbose. 3. Selfreducible languages, where the language and its complement are strongly 2membership comparable, are in P. This generalizes the corresponding result for pselective languages of [9]. 4. Disjunctively truthtable selfreducible languages which are 2membership comparable are in UP. Topic: Structural complexity 1
Abstract Regular Frequency Computations ⋆
"... An (m, n)computation of a function f is given by a deterministic Turing machine which on n pairwise different inputs produces n output values where at least m of the n values are in accordance with f. In such a case we say that the Turing machine computes f with frequency ≥ m/n. The most prominent ..."
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An (m, n)computation of a function f is given by a deterministic Turing machine which on n pairwise different inputs produces n output values where at least m of the n values are in accordance with f. In such a case we say that the Turing machine computes f with frequency ≥ m/n. The most prominent result for frequency computations is due to Trakhtenbrot: The class of (m, n)computable functions equals the class of computable functions if and only if 2m> n. Via characteristic functions the definition of (m, n)computability carries over to sets. Here Trakhtenbrot’s result reads as: The class of (m, n)computable sets equals the class of recursive sets if and only if 2m> n. The notion of frequency computation can be extended to other models of computation. For resource bounded computations, the behavior is completely different: E.g., whenever n ′ − m ′> n − m, it is known that under any reasonable resource bound there are sets (m ′ , n ′)computable, but not (m, n)computable. However, scaling down to finite automata, the analogue of Trakhtenbrot’s result holds again: We show here that the class of languages (m, n)recognizable by deterministic finite automata equals the class of regular languages if and only if 2m> n. This was originally stated by Kinber, but his proof has a flaw, as pointed out by Tantau. Conversely, for 2m ≤ n, the class of languages (m, n)recognizable by deterministic finite automata is uncountable for a twoletter alphabet. When restricted to a oneletter alphabet, then every (m, n)recognizable language is regular. This was also shown by Kinber. We give a new and more direct proof for this result. ⋆ A preliminary version of this work appeared in [1].