mersenneforum.org - View Single Post - trying to implement block lanczos on GF2...

jasonp · 2020-10-05, 15:06

You figured it out, but yes the block Lanczos algorithm finds the nullspace of A^T*A and not of A, since the algorithm only works for symmetric matrices.To get the answers you need, Gauss elimination of the nullspace vectors you have is necessary.

I remember how great it felt when I managed to get the code running on a real problem, BL is hard to figure out from papers, or even from other people's code.

2020-10-05, 15:06	#4
jasonp Tribal Bullet Oct 2004 2·3·19·31 Posts	You figured it out, but yes the block Lanczos algorithm finds the nullspace of A^TA and not of A, since the algorithm only works for symmetric matrices.To get the answers you need, Gauss elimination of the nullspace vectors you have is necessary. I remember how great it felt when I managed to get the code running on a real problem, BL is hard* to figure out from papers, or even from other people's code.