implement highly reliable peer-to-peer systems. In particular, we are comparing the use of whole object and blocking replication, and pursuing the use of erasure codes with blocking replication as a novel technique for achieving high reliability even for systems primarily composed of hosts with poor availability. In this paper, we briefly present the different replication strategies we are exploring, how those strategies can be influenced by application characteristics and host availability, and some preliminary simulation results.

Recent studies have suggested that the soft-error rate in microprocessor logic will become a reliability concern by 2010. This paper proposes an e#cient error detection technique, called fingerprinting, that detects di#erences in execution across a dual modular redundant (DMR) processor pair. Fingerprinting summarizes a processor's execution history in a hash-based signature; di#erences between two mirrored processors are exposed by comparing their fingerprints. Fingerprinting tightly bounds detection latency and greatly reduces the interprocessor communication bandwidth required for checking. This paper presents a study that evaluates fingerprinting against a range of current approaches to error detection. The result of this study shows that fingerprinting is the only error detection mechanism that simultaneously allows high-error coverage, low error detection bandwidth, and high I/O performance.

We construct new self-dual and isodual codes over the integers modulo 4. The binary images of these codes under the Gray map are nonlinear, but formally self-dual. The construction involves Hensel lifting of binary cyclic codes. Quaternary quadratic residue codes are obtained by Hensel lifting of the classical binary quadratic residue codes. Repeated Hensel lifting produces a universal code defined over the 2-adic integers. We investigate the connections between this universal code and the codes defined over Z 4 , the composition of the automorphism group, and the structure of idempotents over Z 4 . We also derive a square root bound on the minimum Lee weight, and explore the connections with the finite Fourier transform. Certain self-dual codes over Z 4 are shown to determine even unimodular lattices, including the extended quadratic residue code of length q + 1, where q j \Gamma1(mod 8) is a prime power. When q = 23, the quaternary Golay code determines the Leech lattice in this way....

This paper explores in detail the use of Error Correcting Output Coding (ECOC) for learning text classifiers. We show that the accuracy of a Naive Bayes Classifier over text classification tasks can be significantly improved by taking advantage of the error-correcting properties of the code. We also explore the use of different kinds of codes, namely Error-Correcting Codes, Random Codes, and Domain and Data-specific codes and give experimental results for each of them. The ECOC method scales well to large data sets with a large number of classes. Experiments on a real-world data set show a reduction in classification error by up to 66% over the traditional Naive Bayes Classifier. We also compare our empirical results to semitheoretical results and find that the two closely agree. 1. Introduction Text Classification is the problem of grouping text documents into classes or categories. For the purpose of this paper, we define classification as categorizing documents in...

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. The main theme of this paper is to take inspiration from methods used in computer science and related disciplines, and to apply these to develop improved biotechnology. In particular, our proposed improvements are made by adapting various information theoretic coding techniques which originate in computational and information processing disciplines, but which we re-tailor to work in the biotechnology context. (a) We apply Error-Correcting Codes, developed to correct transmission errors in electronic media, to decrease (in certain contexts, optimally) error rates in optically-addressed DNA synthesis (e.g., of DNA chips). (b) We apply Vector-Quantization (VQ) Coding techniques (which were previously used to cluster, quantize, and compress data such as speech and images) to improve I/O rates (in certain contexts, optimally) for transformation of electronic data to and from DNA with bounded error. (c) We also apply VQ Coding techniques, some of which hierarchically cluster ...

Erasure codes provide space-optimal data redundancy to protect against data loss. A common use is to reliably store data in a distributed system, where erasure-coded data are kept in different nodes to tolerate node failures without losing data. In this paper, we propose a new approach to maintain ensure-encoded data in a distributed system. The approach allows the use of space efficient  -small. Concurrent updates and accesses to data are highly optimized: in common cases, they require no locks, no two-phase commits, and no logs of old versions of data. We evaluate our approach using an implementation and simulations for larger systems.

. In this paper we discuss the status of the classication of the extremal additive codes over GF (4) which are self-dual under the trace inner product. These codes are of interest because of their connection to quantum codes. There are 5 inequivalent codes of length 8, 8 of length 9, at least 56 of length 10, and exactly 1 of length 11. We discuss the methods of classication, the concepts of lengthening and shortening, and connections to binary codes. 1. Introduction An additive code C over GF (4) of length n is an additive subgroup of GF (4) n . As C is a free GF(2)-module, it has size 2 k for some 0 k 2n. We call C an (n; 2 k ) code. It has a basis, as a GF(2)-module, consisting of k basis vectors; a generator matrix of C will be a k n matrix with entries in GF (4) whose rows are a basis of C. Interest in additive codes over GF (4) has arisen because of their correspondence to quantum codes as described in [3]. There is a natural inner product arising from the trace m...

Aggressive process scaling and increasing clock rates have made crosstalk noise an important issue in VLSI design. Switching on adjacent wires on long bus lines can increase delays and lead to logic faults, particularly when adjacent lines switch with opposite transitions. At the same time system-level interconnects have also become more susceptible to other less predictable forms of interference such as noise induced by power grid fluctuations, electromagnetic interference, and alpha particle radiation. Previous work has treated these systematic and non-systematic forms of noise separately. In this paper we propose to make system level interconnects more robust using encoding that simultaneously addresses error correction requirements and crosstalk noise avoidance. This is more efficient than satisfying these requirements separately. We give algorithms for obtaining optimal encodings, and present a practical class of codes called boundary shift codes. We evaluate the overhead of our method and make comparisons to using error correction with simple shielding.

We give a new proof of the Mallows-Sloane bound on the minimum distance of doubly-even self-dual codes. The proof avoids using the Gleason theorem and invariant theory. It is based on a special choice of the polynomial in the conventional linear programming approach. Keywords: Self-dual codes. 1. Introduction A self-dual linear code C (of length n and minimum distance d) is doublyeven if all its weights are divisible by 4. Let B = (B 0 ; B 1 ; . . . ; B n ) stand for the distance distribution of the code C. It is invariant under MacWilliams transform jCjB i = n X j=0 B j P i (j); (1) where P i is the corresponding Krawtchouk polynomial of degree i, P i (x) = P i k=0 (01) k i x k ji n0x i0k j (for properties of Krawtchouk polynomials see e.g. [4, 6, 7, 8]). Self-dual codes attract a great deal of attention, see many references in [1, 8, 11]. Most of the results are based on an involved machinery of invariant theory. In this paper we prove basic results about self-dual co...