On May 2, 4:14 pm, rjf <fate...@gmail.com> wrote: > I repeat, > > The interesting cases are obvious those which are not covered.
Sorry, I don't know what you mean. Are you saying that by definition they are interesting because they are not covered by Joris' algorithm, whatever they may be? > > I don't know what your fix is, nor do I especially care, but I gather > that, now, at least your "stable" word is meant to indicate something > like a small bound in the maximum over all coefficients of the > difference in relative error between the true result and the computed > result. That sounds reasonable as a definition to me. However it isn't precisely the measure Joris defines. > I have no reason to believe this is an especially relevant measure, > since some coefficients (especially the first and the last) are > probably far more important and, incidentally, far easier to compute. > > Here are some more cases. > > p= (x+1)*(sum(x^i,i,1,n) > q= (x-1)*sum((-1)^i*x^i,i,1,n) > > pick large n. p and q each have n+1 terms. > p*q has 4 non-zero terms, I think. > Thanks. I need to clean my code up and reimplement part of it, now that I know what I am doing. When I get it done, I'll try this out and see if it works. I believe this will work just fine. > Though perhaps this is testing the same issue. > > Here is another > > p=1.7976931348623157E308; > q= 10*x > > What do you do when the coefficients overflow? I actually don't understand what you mean. Why would there be an overflow? I'm missing something important here. I'm using floating point and the exponents can be 64 bits or something like that. There should be no overflow. What do you want the answer to be? Even Sage manages this just fine. > > You might also try arithmetic using the classic > > product((x-i),i,1,n). OK, another interesting one to try when I finish rewriting the code. This again should be handled just fine. Thanks, Bill. > > RJF > > -- > To post to this group, send an email to sage-devel@googlegroups.com > To unsubscribe from this group, send an email to > sage-devel+unsubscr...@googlegroups.com > For more options, visit this group athttp://groups.google.com/group/sage-devel > URL:http://www.sagemath.org -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
