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arXiv 1601.06153cs.ITmath.IT
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非等域码

Codes with Unequal Locality

Swanand Kadhe, Alex Sprintson

摘要:

对于码$\code$,如果其值可以通过访问$\code$的某些其它$r$符号来恢复,则称其第$i$个符号具有局部性$r$。局部可修复码(LRC)是指每个符号都具有局部性$r$的码族。在本文中,我们专注于(线性)码的各个符号可以被划分成不相交的子集,使得在一个子集中的符号有不同的地方比其他的符号。我们称这种码为“非等域码”。对于具有“不相等信息局部性”的码,我们计算了作为每个局部性的信息符号数的函数的最小距离的紧上界。我们证明了金字塔码的构造可以适用于设计具有不相等信息局部性的代码,以实现最小距离界。这一结果推广了Gopalan等人关于具有不等局部性码的经典结果。其次,我们考虑“所有符号位置不相等”的码,并建立一个最小距离的上界作为每个位置的符号数的函数。我们表明,由Silberstein等人的秩度量码的基础上的建设。可以适应获得代码与不平等的所有符号的局部性,实现最小距离界。最后,我们引入了代码的“局部性要求”的概念,它可以被看作是符号的可恢复性要求。代码的信息局部性要求本质上规定了代码中必须存在的不同局部性的信息符号的最小数量。我们提出了一个贪心算法,分配位置的信息符号,以最大限度地提高所有代码之间的最小距离,满足给定的局部性要求。

英文摘要:

For a code $\code$, its $i$-th symbol is said to have locality $r$ if its value can be recovered by accessing some other $r$ symbols of $\code$. Locally repairable codes (LRCs) are the family of codes such that every symbol has locality $r$. In this paper, we focus on (linear) codes whose individual symbols can be partitioned into disjoint subsets such that the symbols in one subset have different locality than the symbols in other. We call such codes as "codes with unequal locality". For codes with "unequal information locality", we compute a tight upper bound on the minimum distance as a function of number of information symbols of each locality. We demonstrate that the construction of Pyramid codes can be adapted to design codes with unequal information locality that achieve the minimum distance bound. This result generalizes the classical result of Gopalan et al. for codes with unequal locality. Next, we consider codes with "unequal all symbol locality", and establish an upper bound on the minimum distance as a function of number of symbols of each locality. We show that the construction based on rank-metric codes by Silberstein et al. can be adapted to obtain codes with unequal all symbol locality that achieve the minimum distance bound. Finally, we introduce the concept of "locality requirement" on a code, which can be viewed as a recoverability requirement on symbols. Information locality requirement on a code essentially specifies the minimum number of information symbols of different localities that must be present in the code. We present a greedy algorithm that assigns localities to information symbols so as to maximize the minimum distance among all codes that satisfy a given locality requirement.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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