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From: Mostafa on 27 Sep 2009 14:58
How to find the inverse of a binary Matrix A ,
Note that the summation is replaced by xor operation.
searching for another matrix B such that A*B=I ( with xor instead of summation) is not efficient, is there another solutions ???
From: Stefano on 27 Sep 2009 15:16
"Mostafa " <mmmedra(a)yahoo.com> wrote in message <h9ocjr$9ai$1(a)fred.mathworks.com>...
> How to find the inverse of a binary Matrix A ,
> Note that the summation is replaced by xor operation.
> searching for another matrix B such that A*B=I ( with xor instead of summation) is not efficient, is there another solutions ???

if you have to solve the general problem, use forward and backward gauss elimination (no pivoting is needed, very easy to code) on the matrix [A, I] obtaining [I, invA]
else, if you are looking for efficient encoding of ldpc codes... google for some paper
From: Mostafa on 29 Sep 2009 15:54
"Stefano " <s.mangione(a)gmail.com> wrote in message <h9odlj$itj$1(a)fred.mathworks.com>...
> "Mostafa " <mmmedra(a)yahoo.com> wrote in message <h9ocjr$9ai$1(a)fred.mathworks.com>...
> > How to find the inverse of a binary Matrix A ,
> > Note that the summation is replaced by xor operation.
> > searching for another matrix B such that A*B=I ( with xor instead of summation) is not efficient, is there another solutions ???
>
> if you have to solve the general problem, use forward and backward gauss elimination (no pivoting is needed, very easy to code) on the matrix [A, I] obtaining [I, invA]
> else, if you are looking for efficient encoding of ldpc codes... google for some paper


you are speaking about the inversion of the normal matrix , I am speaking about the binary one.
From: Stefano on 29 Sep 2009 16:33
No, I'm really speaking about the binary one :)
Don't use the xor() function, it's very slow, use mod( ,2) instead.

Stefano

"Mostafa " <mmmedra(a)yahoo.com> wrote in message <h9tokq$ir6$1(a)fred.mathworks.com>...

> you are speaking about the inversion of the normal matrix , I am speaking about the binary one.
From: Mostafa on 4 Oct 2009 11:33
"Stefano " <s.mangione(a)gmail.com> wrote in message <h9tqtt$njm$1(a)fred.mathworks.com>...
> No, I'm really speaking about the binary one :)
> Don't use the xor() function, it's very slow, use mod( ,2) instead.
>
> Stefano
>
> "Mostafa " <mmmedra(a)yahoo.com> wrote in message <h9tokq$ir6$1(a)fred.mathworks.com>...
>
> > you are speaking about the inversion of the normal matrix , I am speaking about the binary one.


How then ?

could you write a some code?
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