"William Stein" <[EMAIL PROTECTED]> writes: > On 7/24/07, Nick Alexander <[EMAIL PROTECTED]> wrote: >> "Alec Mihailovs" <[EMAIL PROTECTED]> writes: >> >> > May I suggest to add timing to the examples in the documentation - that >> > would be very useful. >> > >> > For example, in recent discussion about Bell numbers on the math-fun list, >> > it was noted that it takes a very long time to calculate bell(1000) in >> > Maple >> > while BellB[1000] in Mathematica is much faster. I looked at the >> > corresponding section in SAGE Reference manual, >> > >> > http://modular.math.washington.edu/sage/doc/html/ref/module-sage.combinat.combinat.html >> > >> > and couldn't tell how much time it takes in SAGE (probably, rather long, >> > because it wraps GAP's Bell.) >> >> sage: sage.combinat.expnums.expnums(10, 1) >> [1, 1, 2, 5, 15, 52, 203, 877, 4140, 21147] >> >> for computing Bell numbers quickly. It's not asymptotically faster >> than Gap, but it is fairly tuned. > > Nick, > > On this topic, SAGE's bell_number command currently still *calls* > GAP. It seems to me it should call your expnums function. What > do you think? Should it cache answers? Thoughts? Basically > I want to improve SAGE's bell_number command so it isn't so slow > by using your expnums function. Also, I wonder what the memory > issues are.
bell_number probably should call expnums. Answers are already cached by expnums. There is a tuning improvement to be made: by doubling the amount of storage required, you can save recomputing the first n when you ask for the first n+k. Asymptotically, that makes no difference, but I could implement it anyway. Nick --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
