Matrix inversion tool

[Oleg Goldshmidt]

Matan Ziv-Av <matan at svgalib.org> writes:

> On Sat, 8 Aug 2015, Omer Zak wrote:
>
>> What happens if you use the regular matrix inversion tool which works
>> on real numbers?  (after rejecting, as singular over Z2, matrices
>> whose determinant modulo 2 is different from 1)
>
> This will work if the inverse only has integer entries. It may also
> work if your algorithm returns rational numbers, but will not work
> with floating point numbers (there are no reals in a computer). You
> cannot faithfully convert 1.1234 to an element of Z_2.

The original matrix contains zeros and ones, and you never need to
divide, just multiply and add modulo 2. 

-- 
Oleg Goldshmidt | pub at goldshmidt.org