Results 1  10
of
22
Designing Programs That Check Their Work
, 1989
"... A program correctness checker is an algorithm for checking the output of a computation. That is, given a program and an instance on which the program is run, the checker certifies whether the output of the program on that instance is correct. This paper defines the concept of a program checker. It d ..."
Abstract

Cited by 307 (17 self)
 Add to MetaCart
A program correctness checker is an algorithm for checking the output of a computation. That is, given a program and an instance on which the program is run, the checker certifies whether the output of the program on that instance is correct. This paper defines the concept of a program checker. It designs program checkers for a few specific and carefully chosen problems in the class FP of functions computable in polynomial time. Problems in FP for which checkers are presented in this paper include Sorting, Matrix Rank and GCD. It also applies methods of modern cryptography, especially the idea of a probabilistic interactive proof, to the design of program checkers for group theoretic computations. Two strucural theorems are proven here. One is a characterization of problems that can be checked. The other theorem establishes equivalence classes of problems such that whenever one problem in a class is checkable, all problems in the class are checkable.
PSelective Sets, and Reducing Search to Decision vs. SelfReducibility
, 1993
"... We obtain several results that distinguish selfreducibility of a language L with the question of whether search reduces to decision for L. These include: (i) If NE 6= E, then there exists a set L in NP \Gamma P such that search reduces to decision for L, search does not nonadaptively reduces to de ..."
Abstract

Cited by 39 (9 self)
 Add to MetaCart
We obtain several results that distinguish selfreducibility of a language L with the question of whether search reduces to decision for L. These include: (i) If NE 6= E, then there exists a set L in NP \Gamma P such that search reduces to decision for L, search does not nonadaptively reduces to decision for L, and L is not selfreducible. Funding for this research was provided by the National Science Foundation under grant CCR9002292. y Department of Computer Science, State University of New York at Buffalo, 226 Bell Hall, Buffalo, NY 14260 z Department of Computer Science, State University of New York at Buffalo, 226 Bell Hall, Buffalo, NY 14260 x Research performed while visiting the Department of Computer Science, State University of New York at Buffalo, Jan. 1992Dec. 1992. Current address: Department of Computer Science, University of ElectroCommunications, Chofushi, Tokyo 182, Japan.  Department of Computer Science, State University of New York at Buffalo, 226...
Lower Bounds for the Low Hierarchy
"... this paper. The low hierarchy, as defined in [Sc83], can only be used to classify the complexity of sets in NP. In order to talk about related sets that are not in NP, the extended low hierarchy was introduced in [BBS86]. (The levels of this hierarchy are labeled EL 2 ,EL 2 , A preliminary ver ..."
Abstract

Cited by 33 (3 self)
 Add to MetaCart
this paper. The low hierarchy, as defined in [Sc83], can only be used to classify the complexity of sets in NP. In order to talk about related sets that are not in NP, the extended low hierarchy was introduced in [BBS86]. (The levels of this hierarchy are labeled EL 2 ,EL 2 , A preliminary version of this paper was presented at the 16th International Colloquium on Automata, Languages, and Programming [AH89a]
NPhard Sets are PSuperterse Unless R = NP
, 1992
"... A set A is pterse (psuperterse) if, for all q, it is not possible to answer q queries to A by making only q \Gamma 1 queries to A (any set X). Formally, let PF A qtt be the class of functions reducible to A via a polynomialtime truthtable reduction of norm q, and let PF A qT be the class of ..."
Abstract

Cited by 27 (5 self)
 Add to MetaCart
A set A is pterse (psuperterse) if, for all q, it is not possible to answer q queries to A by making only q \Gamma 1 queries to A (any set X). Formally, let PF A qtt be the class of functions reducible to A via a polynomialtime truthtable reduction of norm q, and let PF A qT be the class of functions reducible to A via a polynomialtime Turing reduction that makes at most q queries. A set A is pterse if PF A qtt 6` PF A (q\Gamma1)T for all constants q. A is psuperterse if PF A qtt 6` PF X qT for all constants q and sets X . We show that all NPhard sets (under p tt reductions) are psuperterse, unless it is possible to distinguish uniquely satisfiable formulas from satisfiable formulas in polynomial time. Consequently, all NPcomplete sets are psuperterse unless P = UP (oneway functions fail to exist), R = NP (there exist randomized polynomialtime algorithms for all problems in NP), and the polynomialtime hierarchy collapses. This mostly solves the main open...
On Coherence, RandomSelfReducibility, and SelfCorrection
 In Proc. 11th Conference on Computational Complexity
, 1997
"... . We study three types of selfreducibility that are motivated by the theory of program verification. A set A is randomselfreducible if one can determine whether an input x is in A by making random queries to an Aoracle. The distribution of each query may depend only on the length of x. A set B i ..."
Abstract

Cited by 12 (6 self)
 Add to MetaCart
. We study three types of selfreducibility that are motivated by the theory of program verification. A set A is randomselfreducible if one can determine whether an input x is in A by making random queries to an Aoracle. The distribution of each query may depend only on the length of x. A set B is selfcorrectable over a distribution D if one can convert a program that is correct on most of the probability mass of D to a probabilistic program that is correct everywhere. A set C is coherent if one can determine whether an input x is in C by asking questions to an oracle for C \Gamma fxg. We first show that adaptive coherence is more powerful than nonadaptive coherence, even if the nonadaptive querier is nonuniform. Blum et al. [Blum, Luby and Rubinfeld, Journal of Computer and System Sciences, 59:549595, 1993] showed that every randomselfreducible function is selfcorrectable. It is unknown, however, whether selfcorrectability implies randomselfreducibility. We show, under ...
Biimmunity Results for Cheatable Sets
 Theoretical Computer Science
, 1995
"... An oracle A is kcheatable if there is a polynomialtime algorithm to determine the answers to 2 k parallel queries to A from the answers to only k queries to some other oracle B. It is known that 1cheatable sets cannot be biimmune for P. In contrast, we construct 2cheatable sets that are biim ..."
Abstract

Cited by 10 (6 self)
 Add to MetaCart
An oracle A is kcheatable if there is a polynomialtime algorithm to determine the answers to 2 k parallel queries to A from the answers to only k queries to some other oracle B. It is known that 1cheatable sets cannot be biimmune for P. In contrast, we construct 2cheatable sets that are biimmune for arbitrary time complexity classes. In addition, for each k, we construct a set that is (k + 1)cheatable, but not kcheatable; we show that this separation does not hold with biimmunity. We show that if a recursive set A is biimmune for P then there exists an infinite 1cheatable set that is polynomialtime mreducible to A. Consequently if NP contains a set that is biimmune for P then NP contains a set that is not polynomialtime Turingequivalent to a selfreducible set. 1. Introduction Complexity theory deals with how hard problems are. Time, space, and alternation have served as measures of difficulty. Recently, researchers have Research supported by a Fannie and John Hertz ...
On the limitations of locally robust positive reductions
 International Journal of Foundations of Computer Science
, 1991
"... Polynomialtime positive reductions, as introduced by Selman, are by definition globally robust — they are positive with respect to all oracles. This paper studies the extent to which the theory of positive reductions remains intact when their global robustness assumption is removed. We note that tw ..."
Abstract

Cited by 10 (1 self)
 Add to MetaCart
Polynomialtime positive reductions, as introduced by Selman, are by definition globally robust — they are positive with respect to all oracles. This paper studies the extent to which the theory of positive reductions remains intact when their global robustness assumption is removed. We note that twosided locally robust positive reductions — reductions that are positive with respect to the oracle to which the reduction is made — are sufficient to retain all crucial properties of globally robust positive reductions. In contrast, we prove absolute and relativized results showing that onesided local robustness fails to preserve fundamental properties of positive reductions, such as the downward closure of NP. Keywords: Structural complexity theory; Polynomialtime reductions; Complexity classes.
Polynomial time quantum computation with advice
 Inform. Proc. Lett., 90:195–204, 2003. ECCC
"... Abstract. Advice is supplementary information that enhances the computational power of an underlying computation. This paper focuses on advice that is given in the form of a pure quantum state. The notion of advised quantum computation has a direct connection to nonuniform quantum circuits and tall ..."
Abstract

Cited by 10 (1 self)
 Add to MetaCart
Abstract. Advice is supplementary information that enhances the computational power of an underlying computation. This paper focuses on advice that is given in the form of a pure quantum state. The notion of advised quantum computation has a direct connection to nonuniform quantum circuits and tally languages. The paper examines the influence of such advice on the behaviors of an underlying polynomialtime quantum computation with boundederror probability and shows a power and a limitation of advice. Key Words: computational complexity, quantum circuit, advice function 1
On helping and interactive proof systems
 International Journal of Foundations of Computer Science
, 1995
"... We investigate the complexity of honest provers in interactive proof systems. This corresponds precisely to the complexity of oracles helping the computation of robust probabilistic oracle machines. We obtain upper bounds for languages in FewEXP and for sparse sets in NP. Further, interactive protoc ..."
Abstract

Cited by 9 (3 self)
 Add to MetaCart
We investigate the complexity of honest provers in interactive proof systems. This corresponds precisely to the complexity of oracles helping the computation of robust probabilistic oracle machines. We obtain upper bounds for languages in FewEXP and for sparse sets in NP. Further, interactive protocols with provers that are reducible to sets of low information content are considered. Specifically, if the verifier communicates only with provers in P=poly, then the accepted language is low for \Sigma p 2. In the case that the provers are polynomialtime reducible to logsparse sets or to sets in strongP/log then the protocol can be simulated by the verifier even without the help of provers. As a consequence we obtain new collapse results under the assumption that intractable sets reduce to sets with low information content. 1 Introduction and overview of results Two extensions of the concept of NP (as the class of languages with efficient proofs of
Promise Problems and Access to Unambiguous Computation
, 1992
"... This paper studies the power of three types of access to unambiguous computation: nonadaptive access, faulttolerant access, and guarded access. (1) Though for NP it is known that nonadaptive access has exponentially terse adaptive simulations, we show that UP has no such relativizable simulations: ..."
Abstract

Cited by 7 (0 self)
 Add to MetaCart
This paper studies the power of three types of access to unambiguous computation: nonadaptive access, faulttolerant access, and guarded access. (1) Though for NP it is known that nonadaptive access has exponentially terse adaptive simulations, we show that UP has no such relativizable simulations: there are worlds in which (k + 1)truthtable access to UP is not subsumed by kTuring access to UP. (2) Though faulttolerant access (i.e., "lhelping" access) to NP is known to be no more powerful than NP itself, we give both structural and relativized evidence that fault tolerant access to UP suffices to recognize even sets beyond UP. Furthermore, we completely characterize, in terms of locally positive reductions, the sets that faulttolerantly reduce to UP. (3) In guarded access, Grollmann and Selman's natural notion of access to unambiguous computation, a deterministic polynomialtime Turing machine asks questions to a nondeterministic polynomialtime Turing machine in such a way that the nondeterministic machine never accepts ambiguously. In contrast to guarded access, the standard notion of access to unambiguous computation is that of access to a set that is uniformly unambiguouseven for queries that it never will be asked by its questioner, it must be unambiguous. We show that these notions, though the same for nonadaptive reductions, differ for Turing and strong nondeterministic reductions.