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Subject: Re: [ublas] BOOST_UBLAS_USE_ITERATING vs lu_factorize: broken?
From: Paul C. Leopardi (paul.leopardi_at_[hidden])
Date: 2009-08-07 20:58:52

On Wed, 5 Aug 2009, Gunter Winkler wrote:
> Paul C. Leopardi schrieb:
> > Has anyone checked lu_factorize with -DBOOST_UBLAS_USE_ITERATING?
> > It's giving me stranger results. I'm using Boost 1.37.0 with g++ 4.4.0.
> > Best, Paul
> A similar problem occurred some time ago, see
> maybe the
> patch did not fix everything?
> The output is difficult to understand. What is the expected result?

Thanks for your reply.

The expected result is the result without BOOST_UBLAS_USE_ITERATING. Notice
that without BOOST_UBLAS_USE_ITERATING, the expression B/B causes debug
prints of AT, BT, LU and XT (twice), with a result of 1 (ie. the identity

With BOOST_UBLAS_USE_ITERATING, the only debug print is for AT and the result
is NaN. This means that ublas::lu_factorize(LU, pvector) is returning a
non-zero result, indicating that the matrix is singular.
Best, Paul