An extremal self-dual doubly-even binary (n,k,d) code has a minimum weight d=4/spl lfloor/n/24/spl rfloor/+4. Of such codes with length divisible by 24, the Golay code is the only (24,12,8) code, the extended quadratic residue code is the only known (48,24,12) code, and there is no known (72,36,16) code. One may partition the search for a (48,24,12) self-dual doubly-even code into three cases. A previous search assuming one of the cases found only the extended quadratic residue code. We examine the remaining two cases. Separate searches assuming each of the remaining cases found no codes and thus the extended quadratic residue code is the only doubly-even self-dual (48,24,12) code.

The BLASTP program is a search tool for databases of protein sequences that is widely used by biologists as a first step in investigating new genome sequences. BLASTP finds high-scoring local alignments (q/sub i/q/sub i+1/...q/sub i+k//spl par/s/sub j/s/sub j+1/...s/sub j+k/) without gaps between a query sequence q and sequences s in the database. The score of an alignment is the sum of the scores of individual alignments q/sub i+t//spl par/s/sub j+t/ between amino acids that make up the protein. These individual scores come from a scoring matrix modeling the rate of evolutionary mutation. Here we provide a detailed description of the original program and three separate optimisations to it. BLASTP consists of three steps, that we call neighbourhood construction, hit detection, and hit extension. The three optimisations target hit extension since it accounts for 93% of the execution time. The first optimisation alters the data representation of the query sequence and the related code for indexing the scoring matrix. The second optimisation performs extensions in step-sizes of two rather than one. The third optimisation forstalls the calling of the hit extension step in cases that are unlikely to lead to a high-scoring alignment. Individually the three optimisations show speed ups of 15%, 48%, and 63% respectively.

An attempt at directly constructing a (24, 12, 10) extremal quaternary code is reported. The attempt at directly constructing the generator matrix of the code is detailed. It was found that no such code exists.>

Presents a critical study of two approaches, the classical RC-cut approach and H.T. Kung and M.S. Lam's (Proc. 1984 MIT Conf. Advanced Res. VLSI p.74-83, 1984) RCS-cut approach, for reconfiguring faulty systolic arrays. The amount of cell (processing element) redundancy needed to ensure successful reconfiguration into an n*n array is considered. It is shown that no polynomial bounded redundancy is sufficient for the classical approach, whereas O(n/sup 2/log n) redundancy is sufficient for the Kung and Lams approach. The number of faulty cells that can be tolerated in a given array regardless of their locations is characterized and derived. It is shown that, for both approaches, in almost all cases a square array has better fault tolerance than a rectangular array having the same number of cells. A minimal fault pattern in a 2n*2n array with 3n+1 faults that is not reconfigurable into an n*n array using either of the two approaches is established.>

The problem of restructuring systolic arrays with faulty cells is considered. An approach to derive the required data-flow paths and computational sites is proposed. The data skewing requirement, which must be satisfied to find an input schedule, is also discussed. Algorithms to restructure systolic arrays for three different architectures of processing elements are presented. A systematic method to retime the restructured array using additional programmable delays so that the retimed array satisfies the data skewing requirements is developed.>