Re: [eigen] Specializing max_coeff_visitor for some number types

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

On 07.04.2014 16:23, Christoph Hertzberg wrote:
> Hm, well the question is for a matrix, e.g.,
>    [ (1,1)  row1 ]
>    [ (2,20) row2 ]
> whether
>    row2 - (2,20)/(1,1) * row1
> or
>    row1 - (1,1)/(2,20) * row2
> is better (simplified example). [...]

Using the interval length of x/y vs y/x as a metric, it turns out that 
using the element for which x.lowerBound*x.upperBound is biggest should 
be the best choice (this even elegantly handles the case of different 
signed lower/upper bounds which should never be used as pivot).

Christoph


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Dipl.-Inf., Dipl.-Math. Christoph Hertzberg
Cartesium 0.049
Universität Bremen
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