A fast algorithm for evaluating the matrix polynomial I+A+. . .+A/sup N-1/

D. Westreich (ibid., vol.36, no.1, p.162-4, 1989) gave a practical algorithm for the evaluation of the matrix polynomial I+A+A/sup 2/+. . .+A/sup N-1/, which requires at most 3 log/sub 2/N matrix multiplications. The authors present a new method, which only requires at most 2(log/sub 2/N)-1 matrix multiplications. The listing of a BASIC program is given.<
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