On Jan 22, 2009, at 10:25 PM, kcrisman wrote: > In 3.3.alpha0, the following works fine: > > sage: list= [[i,j] for i in [-3..3] for j in [-3..3]] > sage: [coords for coords in list if (coords[0])^2+(coords[1])^2-1==0] > [[-1, 0], [0, -1], [0, 1], [1, 0]] > > The following doesn't terminate in a reasonable amount of time: > > sage: f(x,y)=x^2+y^2-1 > sage: list= [[i,j] for i in [-3..3] for j in [-3..3]] > sage: [coords for coords in list if f(coords[0],coords[1])==0] > > In the notebook I can't even interrupt it; I have to restart the > worksheet, so maybe there's some horrible recursion going on, but ... > I mean, there are only 49 points to check ... right? What am I doing > wrong in using a function this way?
You could try letting f be a multi-variate polynomial rather than a symbolic maxima expression. sage: R.<x,y> = ZZ[] sage: f = x^2+y^2-1 sage: list= [[i,j] for i in [-3..3] for j in [-3..3]] sage: time [coords for coords in list if f(coords[0],coords[1])==0] CPU times: user 0.01 s, sys: 0.00 s, total: 0.01 s Wall time: 0.01 s [[-1, 0], [0, -1], [0, 1], [1, 0]] Searching an even larger range: sage: list= [[i,j] for i in [-30..30] for j in [-30..30]] sage: time [coords for coords in list if f(coords[0],coords[1])==0] CPU times: user 0.69 s, sys: 0.01 s, total: 0.70 s Wall time: 0.74 s [[-1, 0], [0, -1], [0, 1], [1, 0]] - Robert --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
