I don't see a problem. Tell the user to use RIF if he/she unsure about numerical errors. But numerically unstable expressions are unavoidable in general, there isn't anything that we can do about that besides providing the tools to analyse errors.
On Tuesday, January 20, 2015 at 9:07:17 AM UTC+1, Ralf Stephan wrote: > > Hello, > Sage relies on the user to be aware of precision problems, e.g., > > sage: ex=((x-1)^100).expand() > sage: ex.subs(x=1.1) > 8.06715506374094e14 > sage: ((x-1)^100).subs(x=1.1) > 1.00000000000009e-100 > > > or > > sage: legendre_P(100,1.1) > 1.35153125703123e18 > sage: legendre_P(100,x).expand().subs(x=1.1) > 1.46979621554052e23 > > would earn a shrug from developers because the user should know better > and substitute a value with higher precision. > In ticket #17066 the issue of polynomials is disguised. When implemented, > the user could encounter this: > > sage: hypergeometric([1,-100],[3],0.7) > 0.0278923450568346 > sage: hypergeometric([1,-100],[3],x).subs(x=0.7) > -376.859920391941 > > Should the developer care (after having warned the user in the > documentation)? Please comment. > > http://trac.sagemath.org/ticket/17066 > > Regards, > > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
