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首页> 外文期刊>Computational complexity >CLASSIFYING PROBLEMS ON LINEAR CONGRUENCES AND ABELIAN PERMUTATION GROUPS USING LOGSPACE COUNTING CLASSES
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CLASSIFYING PROBLEMS ON LINEAR CONGRUENCES AND ABELIAN PERMUTATION GROUPS USING LOGSPACE COUNTING CLASSES

机译:使用对数计数类的线性同余和Abel置换组的分类问题

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In this paper we classify the complexity of several problems based on Abelian permutation groups and linear congruences using logspace counting classes. The problems we consider were defined by McKenzie & Cook (1987).rnCentral to our study is the problem LCON: given as input (A,b,q), where A ∈ Z~(m×n) and b ∈ Z~m, the problem is to determine if Ax = b is a feasible system of linear equations over Z_q. We assume that q is given by its prime factorization q = p_1~(e_1)p_2~(e_2) … p_k~(e_k), such that each p_i~(e_i) is tiny (i.e. given in unary). We give a randomized NC2 algorithm for LCON. More precisely, LCON is in the nonuniform class L~(GapL)/poly. As LCON is hard for L~(GapL) we get a fairly tight characterization of LCON in terms of logspace counting classes. We derive the same upper bound for computing a basis for the nullspace of a linear map from Z_q~nto Z_q~m.A number of Abelian permutation group problems studied in McKenzie & Cook (1987) turn out to be logspace Turing equivalent to these linear-algebraic problems. Consequently, the upper and lower bounds also carry over to these problems.
机译:在本文中,我们使用对数空间计数类基于Abelian置换组和线性同余性对几个问题的复杂性进行了分类。我们考虑的问题由McKenzie&Cook(1987)定义。rn研究的核心是问题LCON:作为输入(A,b,q)给出,其中A∈Z〜(m×n)和b∈Z〜m ,问题是要确定Ax = b是否是Z_q上的线性方程组的可行系统。我们假设q由其素数分解q = p_1〜(e_1)p_2〜(e_2)…p_k〜(e_k)给出,使得每个p_i〜(e_i)很小(即,以一元形式给出)。我们给出了LCON的随机NC2算法。更准确地说,LCON是非均匀类L〜(GapL)/ poly。由于LCON很难满足L〜(GapL)的要求,因此我们可以从对数空间计数类的角度对LCON进行严格的描述。我们从Mc_Kenzie&Cook(1987)研究的Abelian置换群问题的Z_q〜n至Z_q〜mA数推导计算线性图的零空间的基础的相同上限,证明是对数空间Turing等效于这些线性代数问题。因此,上限和下限同样会影响这些问题。

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