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Re: [Reduce-algebra-developers] Reduce: problem with package linalg
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From: Rainer S. <rai...@gm...> - 2024-02-27 06:34:07
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You're right, of course. I'm sorry I overlooked that.
I suspect this is caused by a numerical insatbility in the algorithm.
Which means that it will take some time to understand and correct it.
Rainer
On Mon, 26 Feb 2024 at 22:45 +0500, Andrey Ignatenko wrote:
> Hi,
>
> I have tried to run this on rev 6658 and find that REDUCE
> hangs on the line "c:=a/2; svdc:=svd(c);"
>
> Andrey.
>
>
> Rainer Schöpf via Reduce-algebra-developers wrote:
> > Hi,
> >
> > rev 6339 is a bit old (June 2022).
> >
> > I do not see the problem in the current version. Can you please try the
> > latest
> > snapshot (rev 6658, dated 2023-12-18)?
> >
> > Looking at the code of the linalg package I believe it can be made more
> > robust,
> > but this will take some time.
> >
> > Rainer
> >
> >
> > On Fri, 23 Feb 2024 at 20:17 -0000, Prof Tony Roberts via
> > Reduce-algebra-de...:
> >
> > > Hi,
> > >
> > > have run into a problem with package lin_alg (and package sparse
> > > also has similar issues). Can anyone fix?
> > >
> > > Using redcsl (rev 6339) I execute the following script
> > >
> > > on rounded; print_precision 4$
> > > load linalg;
> > > a:=mat((-2,3),(5,7));
> > > svda:=svd(a);
> > > b:=a/3; svdb:=svd(b);
> > > c:=a/2; svdc:=svd(c);
> > > end;
> > >
> > > To get the two different failures for matrices b and c.
> > >
> > > 1: in "tmp.txt"$
> > > [-2 3]
> > > a := [ ]
> > > [5 7]
> > > svda := {
> > > [0.1722 - 0.9851]
> > > [ ]
> > > [0.9851 0.1722 ]
> > > ,
> > > [8.713 0 ]
> > > [ ]
> > > [ 0 3.328]
> > > ,
> > > [0.5257 0.8507 ]
> > > [ ]
> > > [0.8507 - 0.5257]
> > > }
> > > [ - 0.6667 1 ]
> > > b := [ ]
> > > [ 1.667 2.333]
> > > ***** svd: Non-numeric matrix element at position ( 1 , 1 )
> > > Cont? (Y or N)
> > > ?y
> > > [ - 1 1.5]
> > > c := [ ]
> > > [2.5 3.5]
> > >
> > > And then redcsl just hangs, and I have to kill the process. Could
> > > someone advise on a work around (for larger matrices).
> > >
> > > The package sparse also causes similar failure.
> > >
> > > Tony
> > >
> > > --
> > > ---------------------------------------------------------------------
> > > Four books and a toolbox:
> > >
> > > * (2020) Linear Algebra for the 21st Century
> > > Oxford University Press. isbn: 978-0-19-885640-5, 978-0-19-885639-9
> > >
> > https://global.oup.com/academic/product/linear-algebra-for-the-21st-century-9780198856399
> > >
> > > * (2015) Model emergent dynamics in complex systems
> > > SIAM, Philadelphia. isbn: 9781611973556.
> > > https://epubs.siam.org/doi/10.1137/1.9781611973563
> > >
> > > * (2009) Elementary calculus of financial mathematics
> > > SIAM, Philadelphia. isbn: 978-0-898716-67-2.
> > > https://epubs.siam.org/doi/10.1137/1.9780898718225
> > >
> > > * (1994) A one-dimensional introduction to continuum mechanics
> > > World Sci. isbn: 978-981-02-1913-0.
> > >
> > > * (2020) with John Maclean, and J. E. Bunder; Equation-Free
> > > function toolbox for Matlab/Octave.
> > > http://github.com/uoa1184615/EquationFreeGit
> > >
> > > Emeritus Professor A.J. Roberts, FAustMS
> > > School of Mathematical Sciences, University of Adelaide
> > > https://profajroberts.github.io/
> > > mailto:Pro...@pr...
> > > http://orcid.org/0000-0001-8930-1552
> > >
> > >
> > >
> > >
> > > _______________________________________________
> > > Reduce-algebra-developers mailing list
> > > Red...@li...
> > > https://lists.sourceforge.net/lists/listinfo/reduce-algebra-developers
> > >
> > >
> >
> >
> >
> > _______________________________________________
> > Reduce-algebra-developers mailing list
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>
Rainer Schöpf
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