Re: Matrix inversion tool

2015-08-10 Thread Shlomi Fish
Hi Omer, On Mon, Aug 10, 2015 at 8:56 PM, Omer Zak w...@zak.co.il wrote: All those discussions about inverting matrices over Z2 make me curious to know what kind of problems can be solved by inverting such matrices. I suppose that the actual problem, with which Shachar is struggling, is

Re: Matrix inversion tool

2015-08-10 Thread Omer Zak
All those discussions about inverting matrices over Z2 make me curious to know what kind of problems can be solved by inverting such matrices. I suppose that the actual problem, with which Shachar is struggling, is proprietary information. However, is it possible to indicate the kind of problems

Re: Matrix inversion tool

2015-08-10 Thread Matan Ziv-Av
On Mon, 10 Aug 2015, Oleg Goldshmidt wrote: I assure you I read and understood Omer's and your posts. If you go back to my reply you will surely realize that at no point I contradicted you. I just pointed out that you didn't need to divide (by det(A)==1), which would lead to the problem you

Re: Matrix inversion tool

2015-08-10 Thread Shachar Shemesh
On 10/08/15 20:56, Omer Zak wrote: All those discussions about inverting matrices over Z2 make me curious to know what kind of problems can be solved by inverting such matrices. I suppose that the actual problem, with which Shachar is struggling, is proprietary information. However, is it

Re: Matrix inversion tool

2015-08-10 Thread Shachar Shemesh
On 10/08/15 17:32, Matan Ziv-Av wrote: At the end of this message is a python program with simple implementations of both algorithms (Gauss eliminiation and recursive). Run them for sizes 10 to 16 consecuitively to see how the difference between exponential and polynomial is very significant

Re: Matrix inversion tool

2015-08-10 Thread Oleg Goldshmidt
Matan Ziv-Av ma...@svgalib.org writes: Please read what you reply to. I assure you I read and understood Omer's and your posts. If you go back to my reply you will surely realize that at no point I contradicted you. I just pointed out that you didn't need to divide (by det(A)==1), which would

Re: Matrix inversion tool

2015-08-10 Thread Oleg Goldshmidt
Matan Ziv-Av ma...@svgalib.org writes: The last line is wrong. You are right. The naive algorithm, taught to any engineering or science student in the first linear algebra course, is Gauss elimination (also known as LU decomposition in this context). It runs in O(n^3) steps. Note that

Re: Matrix inversion tool

2015-08-10 Thread Shachar Shemesh
On 10/08/15 09:23, Oleg Goldshmidt wrote: A general comment. Asymptotic complexity has its uses but is very rarely relevant in practice. One would probaly need a serious literature search just to find out on what scale asymptotic complexity becomes relevant for a given type of problem, and I

Re: Matrix inversion tool

2015-08-09 Thread Matan Ziv-Av
On Sun, 9 Aug 2015, Oleg Goldshmidt wrote: Matan Ziv-Av ma...@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

Re: Matrix inversion tool

2015-08-09 Thread Matan Ziv-Av
On Sun, 9 Aug 2015, Oleg Goldshmidt wrote: Shachar Shemesh shac...@shemesh.biz writes: Hi all, I'm looking for a tool/code to invert a matrix. So far, this sounds trivial. I have one special requirement. I did not think it was too special, except I could not find anywhere that supplied it.

Re: Matrix inversion tool

2015-08-09 Thread Oleg Goldshmidt
Shachar Shemesh shac...@shemesh.biz writes: Hi all, I'm looking for a tool/code to invert a matrix. So far, this sounds trivial. I have one special requirement. I did not think it was too special, except I could not find anywhere that supplied it. I want the matrix to be over a different

Re: Matrix inversion tool

2015-08-09 Thread Matan Ziv-Av
On Sun, 9 Aug 2015, Shachar Shemesh wrote: I should point out that the simplified matrix I was using to prove to myself that the idea has merit is 20x20 (inversed using state of the art in the vi text editing front). The code I'll actually have to run will be 273x273. The Matrix itself is

Re: Matrix inversion tool

2015-08-09 Thread Matan Ziv-Av
On Sun, 9 Aug 2015, Shachar Shemesh wrote: I should point out that the simplified matrix I was using to prove to myself that the idea has merit is 20x20 (inversed using state of the art in the vi text editing front). The code I'll actually have to run will be 273x273. The Matrix itself is

Re: Matrix inversion tool

2015-08-09 Thread Evgeniy Ginzburg
On Aug 9, 2015 20:15, Matan Ziv-Av ma...@svgalib.org wrote: On Sun, 9 Aug 2015, Shachar Shemesh wrote: I should point out that the simplified matrix I was using to prove to myself that the idea has merit is 20x20 (inversed using state of the art in the vi text editing front). The code I'll

Re: Matrix inversion tool

2015-08-08 Thread Omer Zak
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) On Sat, 2015-08-08 at 20:31 +0300, Shachar Shemesh wrote: Hi all, I'm looking for a tool/code to invert a

Re: Matrix inversion tool

2015-08-08 Thread Matan Ziv-Av
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

Re: Matrix inversion tool

2015-08-08 Thread Yaacov Weiss
On Sat, Aug 8, 2015 at 8:31 PM, Shachar Shemesh shac...@shemesh.biz wrote: I want the matrix to be over a different field (i.e. - not the real numbers). In my particular case, I want it to be over Z2 (zero and one). The top results of a search for Finite Field library look promising.

Re: Matrix inversion tool

2015-08-08 Thread Shachar Shemesh
On 08/08/2015 21:31, Yaacov Weiss wrote: On Sat, Aug 8, 2015 at 8:31 PM, Shachar Shemesh shac...@shemesh.biz wrote: I want the matrix to be over a different field (i.e. - not the real numbers). In my particular case, I want it to be over Z2 (zero and one). The top results of a search

Re: Matrix inversion tool

2015-08-08 Thread Oleg Goldshmidt
Matan Ziv-Av ma...@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