Hey Charles, (CC: sage-devel), On Monday 11 Jun 2012, you wrote: > Hi Martin, > > I have a few SAGE-related questions for you. > > This small patch (against sage 5.0) will make the variety() function > work on ideals of BooleanPolynomials. It essentially adds a few basic > functions that were missing (is_univariate(), variable(1), degree(x), > univariate_polynomial(), ....), and then the existing mechanisms start > working. > > After the patch, this should work: > > sage: R.<x,y,z> = BooleanPolynomialRing(3) > sage: p = [ x*y*z + x*z + y + 1, x*y+x*z+y*z, x+y+z+1 ] > sage: I = ideal(p) > sage: I.variety() > > and give the same result as: > > sage: R.<x,y,z> = GF(2)[] > sage: p = [ x*y*z + x*z + y + 1, x*y+x*z+y*z, x+y+z+1 ] > sage: I = ideal(p) > sage: I.variety() > > However, there is a caveat. The variety() function fails when the > ideal is of positive dimension (which makes sense...). However, over > ideals of BooleanPolynomial, it does not fail (indeed, they are all of > dimension zero), but IT RETURNS A WRONG RESULT. > > For instance, > > sage: R.<x,y,z> = BooleanPolynomialRing(3) > sage: p = [ x*y*z + x*z + y + 1 ] > sage: I = ideal(p) > sage: I.variety() > > returns garbage (x=z=0, y=1 is obviously a solution), while : > > sage: R.<x,y,z> = GF(2)[] > sage: p = [ x*y*z + x*z + y + 1 ] > sage: I = ideal(p) > sage: I.variety() > > fails. What should we do about this ?
I guess we'll have to debug it and fix it? :) We should create a ticket for your patch and fix the issue "there"? > Also, I spotted two other very minor problems. > > a) in pbory.pyx, the .variables() function counts "1" as a variable. > This contradicts the way every other functions behave. I don't seem to understand what you mean, as this works fine: sage: P.<x,y> = BooleanPolynomialRing() sage: x.variables() (x,) sage: (x+1).variables() (x,) > b) in multi_polynomial_libsingular.pyx, line 16865, this is a > TypeError, while the docstring advertize a ValueError > > Are these two details worth tickets/patches ? Yes, we should definitely open tickets and upload patches! Cheers, Martin -- name: Martin Albrecht _pgp: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8EF0DC99 _otr: 47F43D1A 5D68C36F 468BAEBA 640E8856 D7951CCF _www: http://martinralbrecht.wordpress.com/ _jab: martinralbre...@jabber.ccc.de -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
