Re: [eigen] Another LDLt issue |
[ Thread Index |
Date Index
| More lists.tuxfamily.org/eigen Archives
]
- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] Another LDLt issue
- From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
- Date: Mon, 30 Mar 2009 20:23:51 +0200
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type :content-transfer-encoding; bh=92+4PCx0RkJsKyl5uISqgRPAeS42+D0B39R4oNju/yE=; b=nGQ58ymXddTtgnfgOyNi2CXDJS/pXL9Jy2HGKMx7kilO6XY5Fxj4ofydnMBmB5gEDY m8VjU5g2CtJe0zlGcQ+pu/niJ8XQr3yE8IgwPOc3jMyw/TCedaWlP5Gfa7yNAlVP/a16 hIVZxUOFQex5B1pFaarPpGmF+t14BWsYgSNfw=
- Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=bDxvyH4VsusyQuin4Hf4SpUsg9J3h9Uo7UEN8uOuPs7zkEIcHUg1OZdZcmHxsollu7 GMZza0SBcBEJ09Tgk4nOXCoczhrqAzxgFkgFuzqSbhEIB4cP/DRNc0LNWxSAxPlDfY+k KW2pf7vLxik/kZJudrFFp1FWJfC6tP+t9FmAw=
2009/3/30 Bill Greene <w.h.greene@xxxxxxxxx>:
> Are you talking about a case where an LDLt factorization exists but the
> matrix is singular?
> To be honest, before starting this current thread, I didn't even realize
> such a case could
> exist.
By the way, there also are plenty of examples for that. Take any
diagonal matrix D with some zeros. For example D could be the diagonal
matrix with diagonal terms 1,0,0,.....,0. Take L to be the identity
matrix, so L is a triangular matrix with unit diagonal; then you have
LDLt = D, so D has a LDLt factorization yet it is singular and
selfadjoint.
Cheers,
Benoit