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From Greg Sterijevski <gsterijev...@gmail.com>
Subject Re: [math] Backsolve and Frontsolve
Date Wed, 20 Jul 2011 14:46:01 GMT
Gents,

I noticed that QR and LU have this functionality, but I thought it would be
a bit of a hack. I have the 15 lines of code ready. I will submit it.

-Greg

On Wed, Jul 20, 2011 at 12:54 AM, Phil Steitz <phil.steitz@gmail.com> wrote:

> On 7/19/11 9:55 PM, Greg Sterijevski wrote:
> > Hello,
> >
> > I was working on some regression issues when I stumbled into the need to
> > solve a system like
> >
> >   R y = b or R'y = b.
> >
> > R is an upper or lower triangular, b is a vector.
> >
> > Does this functionality exist? If not, can I add it? And where?
>
> As Ted pointed out, you may be able to somewhat awkwardly get what
> you need from either the QR or LU decomp embedded Solver
> implementations.  If you have the need, itch and time, I would be +1
> to cleanly encapsulate direct back/front solving methods (with the
> appropriate zoo of double[] and matrix operands - see the
> DecompositionSolver interface) into either a DirectSolver class or
> as utility methods added to MatrixUtils.  The latter might make
> replacement of the (duplicate) impls in the decomp solvers and other
> applications easier.  Others may have different / better ideas on this.
>
> Phil
> >
> > Thanks,
> >
> > -Greg
> >
>
>
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