Try http://www.cas.mcmaster.ca/~carette/publications/simplification.pdf The real point is that GiNaC's canonical form has different goals from a 'simplify' command in the sense of minimal complexity. One really needs to separate the two, and I don;t know how easy that is with the current design. James On Feb 22, 5:18 pm, Mark Rahner <[email protected]> wrote: > On Feb 22, 2:37 am, JamesHDavenport <[email protected]> wrote:> > "Canonical form" and "simplify" aren't the same thing (necessarily).> > See Carette,J., Understanding Expression Simplification. > Proc. ISSAC > 2004 (ed. J. Gutierrez), ACM Press, New York, 2004, pp. 72-79. > I don't have access to that source but I completely agree, noting that > the passage you quoted discusses the results of full_simplify(). > What I've reported is primarily a bug in Sage simplification. > However, the underlying cause appears to be an issue with the GiNaC > canonical form, which apparently tends to proliferate radicals of > small integers. Given Sage's dependence upon GiNaC's canonical form, > unless Sage aggressively simplifies such expressions, Sage users will > see many more expressions like > -(3*sqrt(-2/3*(2*(3*sqrt(-2*sqrt(5) + 5) - 2*sqrt(5) +3)/ > (sqrt(-2*sqrt(5) + 5) - sqrt(5) + 2) - 3)*el + 1/9*(3*sqrt(-2*sqrt(5)+ > 5) - 2*sqrt(5) + 3)^2/(sqrt(-2*sqrt(5) + 5) - sqrt(5) + 2)^2) - > (3*sqrt(-2*sqrt(5) + 5) - 2*sqrt(5) + 3)/(sqrt(-2*sqrt(5) + 5) - > sqrt(5)+ 2))/(2*(3*sqrt(-2*sqrt(5) + 5) - 2*sqrt(5) + 3)/ > (sqrt(-2*sqrt(5) + 5)- sqrt(5) + 2) - 3) > My system engineering gut feel is that it would be desirable to > address this particular simplification issue closer to the source > rather than to try to engineer around it on the simplification end. > When I get some free time, I'm going to raise this issue on GiNaC- > list. I'm not sure how soon that will be though. > -Mark
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