|Bill Allombert on Tue, 14 Jan 2014 14:35:20 +0100|
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|Re: new FFM_mul (and FlxqM_mul, FqM_mul, ...)|
On Tue, Jan 14, 2014 at 12:32:39PM +0100, Karim Belabas wrote: > * Bill Allombert [2014-01-14 11:48]: > > Do you know how to compute the square of a matrix faster than by using M*M ? > > Obviously for matrices of size 1, we do :-) > > For size 2 as well (2 squares + 4 multiply) : > > (12:15) gp > [a,b;c,d]^2 > %1 = > [a^2 + c*b b*a + d*b] > > [c*a + d*c c*b + d^2] > > = > > [a^2 + c*b b*(a + d)] > > [c*(a + d) c*b + d^2] This is only 2 squares and 3 multiply :) Cheers, Bill.