[godsmokescrack]

The basic idea of reducing 4 multiplications to 3 multiplications

(ax + b)(cx + d) = acx^2 + [(a + b)(c + d) - ac - bd]x + bd

holds pretty generally; there isn't any new math or algorithm here that I can see. Their own complexity analysis (eqns. 7 and 8) shows this performs about the same as using Karatsuba multiplication on the entries of the matrices (instead of on the matrices themselves).

[arcastroe]

> this performs about the same as using Karatsuba multiplication on the entries of the matrices (instead of on the matrices themselves).

If it offers improvements in both, why wouldn't one do it in both?