On Feb 13, 2008 9:57 AM, Nick Alexander <[EMAIL PROTECTED]> wrote: > > > On 13-Feb-08, at 6:06 AM, John Cremona wrote: > > > > > I just discovered sage.rings.arith.discrete_log_generic(), not until > > after implementing a similar function for elliptic curves over finite > > fields (patch to be submitted before too long). I thought it was a > > pity that we cannot apparently use the same code for dlogs in an > > additive group (as in what I just wrote) and a multiplcative one (as > > in discrete_log_generic()). Could we? > > At this time, not easily.
I think it would be trivial. Just pass in a function of two arguments called "mul" instead of using "*". It's the same way Python's sort works. (One should probably also pass in a pow function.) > Some of the categorical work initiated at > SD7 could help with this. The relevant instigator is Nicholas Thiery > and the implementors are, at this time, Robert Bradshaw, David Roe, > and Mike Hansen. (Apologies if I added/dropped anyone.) That sort of complicated stuff would only be necessary maybe for efficiency reasons -- but then you shouldn't be using a generic algorithm. > > > Also, in the code for sage.rings.arith.discrete_log_generic(), which I > > see was written by WIlliam and David Joyner in prehistoric times > > (2005-01-05 must be before the first ever reease of Sage!) there is > > an inefficiency in using an array for g instead of a dict. Shall I > > write a patch for that? > > Please do. Yes, please. That was before I knew about some tricks like that.... > > > > -- William Stein Associate Professor of Mathematics University of Washington http://wstein.org --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com 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://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
