Re: [eigen] Another LDLt issue

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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


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