Tuesday 20 November 2007

LIM (Part 3) - Toom-Cook

Another method of multiplication is called Toom-Cook, first described in 1963.
http://en.wikipedia.org/wiki/Toom-Cook_multiplication
This is basically a generalization of the Karatsuba Method, by splitting the input numbers into multiple parts at a time, rather than just two (as in Karatsuba) or 1 (ie no splitting) (as in classical long multiplication).
Toom-3 (3-way Toom-Cook) reduces 9 multiplications to 5, and runs in order n^(log5/log3) time.

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