On Mon, Dec 15, 2008 at 5:15 PM, M. Yurko <myu...@gmail.com> wrote: > > Sure, here are some examples of what I did: > #First, and example of the bug > Ei(20) > Output: 25615646.4145 + 6.28318530718*I #it should instead be just > 25615646.4145 > > Ei(19) > Output: 9950907.25105 #the error doesn't occur here > > -exponential_integral_1(-20).n(digits=50) > Output: 25615652.664056588 #here the bug doesn't occur, although the > code for exponential_integral_1 loses a lot of accuracy by converting > the number returned from PARI into a float, so i has much less > accuracy > > -pari(-20).eint1().n(digits = 50) > Output: 2.5615652664056588773746625520288944244384765625000e7 #here > the full accuracy from PARI is preserved > > #the following shows the difference in the speed of the two methods > #the current implementation > %time > for i in srange (1,10^6): > num = Ei(10) > Output: CPU time: 51.64 s, Wall time: 51.81 s > > #the time of PARI's implementation > %time > for i in srange (1,10^6): > num = pari(-i).eint1() > Output: CPU time: 20.12 s, Wall time: 20.32 s > #PARI's implementation seems to be more than twice as fast >
A quick remark: The Pari Ei only works with *real* input, whereas the scipy one works with complex input. And yes, somebody should make a trac ticket, then report this upstream. And the Sage function will have to fixed in the meantime or at least as a bare minimum have a big comment at the top explaining that there is a bug. -- William --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
