On 10/27/2012 09:19 PM, Jason Grout wrote:
On 10/27/12 1:04 AM, P Purkayastha wrote:
Until that gets in, I put in a patch at #13657 to the tutorial to at
least mention RDF/CDF as the ones to use for eigenvalue and eigenvector
computations. And possible other numerical computations. If you have
anything more to add, then please do so.
http://trac.sagemath.org/13657
Right now, when you do eigenvalues with RR, it prints a warning. Maybe
you should add something to the actual code too.
sage: a=matrix(RR,3,range(9))
sage: a.eigenvalues()
/Users/grout/sage-trees/sage-5.4.rc1/local/bin/sage-ipython:1:
UserWarning: Using generic algorithm for an inexact ring, which will
probably give incorrect results due to numerical precision issues.
#!/usr/bin/env python
[13.3484692283495, -0.000000000000000, -1.34846922834953]
Mentioning RDF/CDF in that warning might be helpful. You might also add
a warning to Gaussian elimination, at least until we implement pivoting
choices and default to a more numerically sane choice.
Thanks,
Jason
rbeezer had proposed a better solution here:
http://trac.sagemath.org/sage_trac/ticket/12514#comment:7
Unfortunately, I completely forgot about that ticket and haven't gotten
around to making that change.
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