Ok, from this point of view see the point. But I dont know if it's documented this way somewhere.
greatz Am 28.12.2010 23:00, schrieb Iwao Kimura: > Hi Johannes, > > I'm not sure but if we think gcd(2, 0) is the generator of the ideal > generated by 2 and 0 in the rationals, we see gcd(2,0) is 1 because > the ideal is not zero (and QQ is a field :) > > Best regards. > > On Wed, Dec 29, 2010 at 6:33 AM, Johannes <dajo.m...@web.de> wrote: >> I got it solved. It's a type error: >> the matrix sing is a matrix over QQ. >> If its a matrix over ZZ it works fine. >> >> but why is gcd(2,0) = 1 for 2,0 as Rationals? >> in my eyes its not well defined or should be the maximum of those values. >> >> greatz >> >> Am 28.12.2010 22:08, schrieb Johannes: >>> Hi list, >>> I've a very confusing problem with some simple algorithm: >>> >>> following setting: a matrix sing: >>> sage: sing >>> [ 3 0 1] >>> [-2 -1 -2] >>> [ 0 1 0] >>> sage: l = sings.column(2);l >>> (1, -2, 0) >>> #my algorithem, code see below: >>> sage: extgcd(l) >>> #some printoutput for debugging: >>> l: (1, -2, 0) >>> tlist: (-2, 0) >>> #this should not be, d = gcd(tlist) >>> d: 1 >>> l: [1, 1] >>> [u, v]: [0, 1] >>> l: (-2, 0) >>> [u, v]: [1, 0] >>> res: [0, 1, 0] >>> #the result: >>> [0, 1, 0] >>> #now the same but i construct the vector on my own: >>> sage: l = vector([1,-2,0]);l >>> (1, -2, 0) >>> sage: extgcd(l) >>> l: (1, -2, 0) >>> tlist: (-2, 0) >>> #here it works fine >>> d: 2 >>> l: [1, 2] >>> [u, v]: [1, 0] >>> l: (-2, 0) >>> [u, v]: [1, 0] >>> res: [1, 0, 0] >>> #getting the expected result: >>> [1, 0, 0] >>> >>> the code of my algorithm: >>> >>> def extgcd(l): >>> print "l: " + str(l) >>> assert len(l) > 1 >>> >>> if len(l) == 2: >>> #calculated ext euclidean for two values >>> a = l[0] >>> b = l[1] >>> >>> u=t=1 >>> v=s=0 >>> while b>0: >>> q=a//b >>> a, b = b, a-q*b >>> u, s = s, u-q*s >>> v, t = t, v-q*t >>> print "[u, v]: " + str([u, v]) >>> return [u, v] >>> else: >>> >>> #this is the part where it does not work! >>> tlist = l[1:] >>> print "tlist: " + str(tlist) >>> d = gcd(tlist) >>> print "d: " + str(gcd(tlist)) >>> >>> #calculate part decomp >>> u, v = extgcd([l[0],d]) >>> #calculate rest >>> ttlist = extgcd(tlist) >>> res = [u] >>> #combine results >>> res.extend([v * item for item in ttlist]) >>> print "res: " + str(res) >>> return res >>> >>> I hope somebody can help me. >>> greatz Johannes >>> >> >> -- >> 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 >> URL: http://www.sagemath.org >> > > > -- 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 URL: http://www.sagemath.org
