[Numpy-discussion] Problem in LinearAlgebra?
rob at hooft.net
Sun Nov 2 06:51:23 CST 2003
Nadav Horesh wrote:
> I tested the problem with:
> 1. Numeric 23.1 under python 2.3.2
> 2. numarray 0.8 (I made a copy of the Scientific package where all
> calls to Numeric were replaced to numarray), under python 2.3.2
> There results where about the same -- high coefficients for the 5th
> order polynomials.
> I would expect reliable fit for a high order polynomials only under very
> special circumstances, so this is not a big surprise.
Thanks for your efforts.
The polynomial we're trying to fit here is not extremely unstable. As I
said, with Numeric 17.1.2 my class of problems used to be stable up to
at least 9th order. I really suspect a bug was introduced here which is
difficult to pinpoint because everybody reacts the natural way: this is
an intrinsicly unstable problem, so it is not unexpected. Somehow it
could have been better, though!
I managed to work around the problem so far by using a different solver
also built in to Scientific Python, so I am saved so far.
Rob W.W. Hooft || rob at hooft.net || http://www.hooft.net/people/rob/
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