Re: [sage-support] Re: Group action
One thing to watch out for is that the generators returned by automorphism_group contain symbols that may not be the actual vertices. I realised this once after several frustrating hours of bizarre results from my program. I'm not sure if this is still the case in recent versions. Yep. I wasted 30 minutes easily on that one too. Actually the elements are always 1...n regardless of the graph's labelling (which often starts at 0). That's a shame. Nathann -- 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
[sage-support] Re: Integration issue
On 2012-05-14, JamesHDavenport j.h.davenp...@bath.ac.uk wrote: It may be branch cut strangeness, but if so it is very strange. The integrand is clearly well-behaved, and the integral, while in terms of the incomplete gamma function, seems to be off the usual branch cut (negative real axis). Try domain:complex before calling integrate; that changes the result to what I think is expected. I guess (emphasis on guess) that the problem originates not from gamma_incomplete itself but from terms of the form (-1)^(1/n) which are the result of simplifying or evaluating gamma_incomplete. Sorry I can't be more helpful. best, Robert Dodier -- 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
Re: [sage-support] Re: Group action
On Mon, May 14, 2012 at 11:20 PM, Nathann Cohen nathann.co...@gmail.com wrote: One thing to watch out for is that the generators returned by automorphism_group contain symbols that may not be the actual vertices. I realised this once after several frustrating hours of bizarre results from my program. I'm not sure if this is still the case in recent versions. Yep. I wasted 30 minutes easily on that one too. Actually the elements are always 1...n regardless of the graph's labelling (which often starts at 0). That's a shame. This is because permutation groups used to not support arbitrary domains. Since they do now, it should be easy to return an automorphism group that actually acts on the vertices. --Mike -- 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
[sage-support] Re: Making a copy of a MixedIntegerLinearProgram
Hellooo Emil !!! Well, I just tried something and it ended upi crashing Sage, so I can just advise you to create all your variables in the first LP from the start, *then* to copy the MixedIntegerLinearProgram object. Of course it is a bad answer :-) John Perry was the one who needed this copy() feature for MILP and he was doing things similar to the ones you attempt. As I only had integer programs in mind when I wrote this class (hence hard problems to solve. hence the times it takes to generate the LP is totally small compared to the rest) I am totally ready to admit that it is not very suited to such computations. Dima mentionned recently that we may create some LinearProgram class at some point which would be thought *for* this type of problems, but I would fint it hard to write it myself considering that that would not be a user of it Hence no clue of what should be possible or not with it :-) Nathann -- 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
Re: [sage-support] Re: Group action
Well, you can call GAP, e.g. as follows: sage: gap(Orbit(+str(ag._gap_())+,[1,2,7],OnSets);) [ [ 1, 2, 7 ], [ 1, 2, 3 ], [ 1, 6, 9 ], [ 2, 3, 4 ], [ 3, 4, 10 ], [ 1, 6, 8 ], [ 3, 4, 8 ], [ 4, 9, 10 ], [ 4, 7, 9 ], [ 5, 8, 10 ], [ 2, 5, 7 ], [ 5, 6, 8 ], [ 3, 5, 8 ], [ 4, 6, 9 ], [ 5, 7, 10 ], [ 5, 7, 9 ], [ 6, 7, 9 ], [ 3, 6, 8 ], [ 1, 6, 10 ], [ 2, 7, 9 ], [ 1, 2, 10 ], [ 2, 3, 8 ], [ 6, 8, 9 ], [ 1, 5, 10 ], [ 2, 3, 7 ], [ 1, 4, 10 ], [ 5, 7, 8 ], [ 3, 4, 9 ], [ 4, 5, 10 ], [ 1, 2, 6 ] ] THnk you Dima !! I finally got it to work thanks to you Too me some time to find out that Gap would return a totally weird error message if the list you give as an argument is not sorted, and I guess most of the time it takes to run the computation is devoted to translating Gap object to Sage ones afterwards, but It works !! ;- (But Gap definitely has the worst syntax ever) Nathann -- 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
Re: [sage-support] Re: Making a copy of a MixedIntegerLinearProgram
Hi Nathann, Thanks for writing the MILP class - it works very well. Now, I can do: x = lp.new_variable() Is there any way to do something like x = lp.get_existing_variables() ? I'm working on some graph theoretic stuff: I'm solving two LPs for each graph, for as many graphs as I can. - Emil. On 15 May 2012 08:00, Nathann Cohen nathann.co...@gmail.com wrote: By the way, could I ask you what lead you to create and solve many LP ? I mean, what are you solving which requires you to do that ? ^^; Nathann -- 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
[sage-support] Re: Making a copy of a MixedIntegerLinearProgram
On Monday, May 14, 2012 7:32:25 PM UTC-5, Emil wrote: lp = MixedIntegerLinearProgram(maximization=True) x = lp.new_variable() Then I do: nlp = copy(lp) x = nlp.new_variable() The variable 'x' now seems to contain different variables. So I cannot add any constraints that use the existing variables. Or is there some way to do this? Thanks, x *should* contain different variables, for two reasons. First, nlp already has a variable (a copy of the one you created for lp), so if you ask nlp to create a new variable for it, it won't return the variable lp created earlier. Second, after copying lp to nlp, you might want to change some variables in one from real to integer, or vice-versa. Also, I don't think Sage has ever let you create variables add constraints that way. I don't know why, but if I want a variable with a compact notation, I've found MILP lets you do it this way: sage: x, y = lp[0], lp[1] but NOT sage: x, y = lp.new_variable(), lp.new_variable() You'll get variables alright, but you can't add constraints using the second. The first works fine. To add constraints, I usually do the following: sage: lp = MixedIntegerLinearProgram(maximization=False) sage: lp.add_constraint(2*lp[0] + 3*lp[1] = 1) sage: nlp = copy(lp) sage: nlp.add_constraint(3*lp[0] - 2*lp[1] = 1) Or, if you like, use x, y, etc., defining them as I did above (the FIRST way). regards john perry -- 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
[sage-support] Re: Integration issue
It may be branch cut strangeness, but if so it is very strange. The integrand is clearly well-behaved, and the integral, while in terms of the incomplete gamma function, seems to be off the usual branch cut (negative real axis). Try domain:complex before calling integrate; that changes the result to what I think is expected. (%i5) display2d:false; (%o5) false (%i6) integrate(x*cos(x^3),x); (%o6) (gamma_incomplete(2/3,%i*x^3)+gamma_incomplete(2/3,-%i*x^3))/6 (%i7) domain:complex; (%o7) complex (%i8) integrate(x*cos(x^3),x); (%o8) ((sqrt(3)*%i-1)*gamma_incomplete(2/3,%i*x^3) +(-sqrt(3)*%i-1)*gamma_incomplete(2/3,-%i*x^3)) *(x^3)^(1/3) /(12*x) But the *definite* integral in both cases is wrong. Any ideas? (%i1) display2d:false; (%o1) false (%i2) integrate(x*cos(x^3),x,0,1/2); (%o2) gamma_incomplete(2/3,%i/8)/6+gamma_incomplete(2/3,-%i/8)/6-gamma(2/3)/3 (%i3) domain:complex; (%o3) complex (%i4) integrate(x*cos(x^3),x,0,1/2); (%o4) gamma_incomplete(2/3,%i/8)/6+gamma_incomplete(2/3,-%i/8)/6-gamma(2/3)/3 I guess (emphasis on guess) that the problem originates not from gamma_incomplete itself but from terms of the form (-1)^(1/n) which are the result of simplifying or evaluating gamma_incomplete. Sorry I can't be more helpful. I don't see any of those up here, though, and the gamma_incomplete evaluation is correct (gives the same via W|A, Sage = Pari in my version, mpmath, and Maxima). I think that Maxima is somehow using the real antiderivative, if that makes sense - is that possible, 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 URL: http://www.sagemath.org
[sage-support] Re: Integration issue
On Tuesday, May 15, 2012 2:36:34 AM UTC-4, Keshav Kini wrote: John H Palmieri jhpalmier...@gmail.com writes: This works for me: sage: numerical_integral(x*cos(x^3), 0, 0.5) (0.1247560409610376, 1.3850702913602309e-15) Interesting... sage: numerical_integral(x*cos(x^3), 0, 0.5) (0.1247560409610376, 1.3850702913602309e-15) sage: (x*cos(x^3))(0) /opt/sage-5.0.rc1/local/lib/python2.7/site-packages/IPython/iplib.py:2260: DeprecationWarning: Substitution using function-call syntax and unnamed arguments is deprecated and will be removed from a future release of Sage; you can use named arguments instead, like EXPR(x=..., y=...) exec code_obj in self.user_global_ns, self.user_ns 0 Why does numerical_integral() not trigger the deprecation warning? The same reason that plot and integral don't, because we're not calling them in the same way. It makes sense to integrate symbolic expressions and to plot them. It's true that we need to unify our integration command syntax (see http://trac.sagemath.org/sage_trac/ticket/7763). - kcrisman -- 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
Re: [sage-support] Re: Making a copy of a MixedIntegerLinearProgram
Next issue is that the Gurobi backend doesn't support the copy: AttributeError: 'sage.numerical.backends.gurobi_backend.GurobiBacke' object has no attribute 'copy' Any idea how much work this would be to do? (I can now do what I wanted to do before, at least with GLPK.) Emil -- 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
Re: [sage-support] Re: Making a copy of a MixedIntegerLinearProgram
Hellooo !! Next issue is that the Gurobi backend doesn't support the copy: Oops ^^; Any idea how much work this would be to do? Oh, it's usually quite straightforward to implement such things. Usually the feature already exists in the solver's C api, and all the work that needs to be done is to expose it in Sage :-) Nathann -- 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
[sage-support] Re: Integration issue
On 2012-05-15, kcrisman kcris...@gmail.com wrote: (%i3) domain:complex; (%o3) complex (%i4) integrate(x*cos(x^3),x,0,1/2); (%o4) gamma_incomplete(2/3,%i/8)/6+gamma_incomplete(2/3,-%i/8)/6-gamma(2/3)/3 Hmm. I get a different result. I am using the current Git version. domain : complex; integrate (x*cos(x^3), x, 0, 1/2); = %i*gamma_incomplete(2/3,%i/8)/(4*sqrt(3)) -gamma_incomplete(2/3,%i/8)/12-%i*gamma_incomplete(2/3,-%i/8)/(4*sqrt(3)) -gamma_incomplete(2/3,-%i/8)/12+gamma(2/3)/6 expand (float (%)); = .1247560409610377 That's gratifying, but the problem, as I'm sure you know, is that the user won't know they have to change a global variable. I don't see any of those up here, though, and the gamma_incomplete evaluation is correct (gives the same via W|A, Sage = Pari in my version, mpmath, and Maxima). I think that Maxima is somehow using the real antiderivative, if that makes sense - is that possible, Robert? It seems plausible, but I don't know the integration code very well. best Robert Dodier -- 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
Re: [sage-support] Digest for sage-support@googlegroups.com - 25 Messages in 4 Topics
Bonjour Monsieur, je suis nouveau avec le logiciel sage, actuellement j'essaye d'installer la version sage-4.8 sur Ubuntu 12.04 mais j'y arrive pas, s'il vous plait aider moi à faire cette installation. merci. 2012/5/15 sage-support@googlegroups.com Today's Topic Summary Group: http://groups.google.com/group/sage-support/topics - Making a copy of a MixedIntegerLinearProgram#137513d7e049c617_group_thread_0[9 Updates] - Integration issue #137513d7e049c617_group_thread_1 [7 Updates] - Application/Use of Sage in IT company or Industries#137513d7e049c617_group_thread_2[1 Update] - Group action #137513d7e049c617_group_thread_3 [8 Updates] Making a copy of a MixedIntegerLinearProgramhttp://groups.google.com/group/sage-support/t/b84fede6c3081915 Emil emi...@gmail.com May 15 01:32AM +0100 I would like to solve a large number of very similar linear programs. More specifically I would like to be able to 1) Create a MixedIntegerLinearProgram, and add some constraints. 2) Keep this MILP somewhere. 3) (Repeated many times) Take a copy of the saved MILP, add a few more constraints specific to this problem instance, and solve it. The difficulty I have is that I am unclear how to add new constraints that include previous variables. Suppose I do lp = MixedIntegerLinearProgram(maximization=True) x = lp.new_variable() Then I do: nlp = copy(lp) x = nlp.new_variable() The variable 'x' now seems to contain different variables. So I cannot add any constraints that use the existing variables. Or is there some way to do this? Thanks, Emil Nathann Cohen nathann.co...@gmail.com May 14 11:51PM -0700 Hellooo Emil !!! Well, I just tried something and it ended upi crashing Sage, so I can just advise you to create all your variables in the first LP from the start, *then* to copy the MixedIntegerLinearProgram object. Of course it is a bad answer :-) John Perry was the one who needed this copy() feature for MILP and he was doing things similar to the ones you attempt. As I only had integer programs in mind when I wrote this class (hence hard problems to solve. hence the times it takes to generate the LP is totally small compared to the rest) I am totally ready to admit that it is not very suited to such computations. Dima mentionned recently that we may create some LinearProgram class at some point which would be thought *for* this type of problems, but I would fint it hard to write it myself considering that that would not be a user of it Hence no clue of what should be possible or not with it :-) Nathann Nathann Cohen nathann.co...@gmail.com May 15 12:00AM -0700 By the way, could I ask you what lead you to create and solve many LP ? I mean, what are you solving which requires you to do that ? ^^; Nathann Emil emi...@gmail.com May 15 11:47AM +0100 Hi Nathann, Thanks for writing the MILP class - it works very well. Now, I can do: x = lp.new_variable() Is there any way to do something like x = lp.get_existing_variables() ? I'm working on some graph theoretic stuff: I'm solving two LPs for each graph, for as many graphs as I can. - Emil. john_perry_usm john.pe...@usm.edu May 15 05:38AM -0700 On Monday, May 14, 2012 7:32:25 PM UTC-5, Emil wrote: The variable 'x' now seems to contain different variables. So I cannot add any constraints that use the existing variables. Or is there some way to do this? Thanks, x *should* contain different variables, for two reasons. First, nlp already has a variable (a copy of the one you created for lp), so if you ask nlp to create a new variable for it, it won't return the variable lp created earlier. Second, after copying lp to nlp, you might want to change some variables in one from real to integer, or vice-versa. Also, I don't think Sage has ever let you create variables add constraints that way. I don't know why, but if I want a variable with a compact notation, I've found MILP lets you do it this way: sage: x, y = lp[0], lp[1] but NOT sage: x, y = lp.new_variable(), lp.new_variable() You'll get variables alright, but you can't add constraints using the second. The first works fine. To add constraints, I usually do the following: sage: lp = MixedIntegerLinearProgram(maximization=False) sage: lp.add_constraint(2*lp[0] + 3*lp[1] = 1) sage: nlp = copy(lp) sage: nlp.add_constraint(3*lp[0] - 2*lp[1] = 1) Or, if you like, use x, y, etc., defining them as I did above (the FIRST way). regards john perry Emil emi...@gmail.com May 15 02:47PM +0100 I've found MILP lets you do it this way: sage: x, y = lp[0], lp[1] Ahh!
Re: [sage-support] Digest for sage-support@googlegroups.com - 25 Messages in 4 Topics
Bonjour Monsieur, je suis nouveau avec le logiciel sage, actuellement j'essaye d'installer la version sage-4.8 sur Ubuntu 12.04 mais j'y arrive pas, s'il vous plait aider moi à faire cette installation. merci. Can one of our French-speaking folks help this gentleman? We already have great relations with AIMS in South Africa, and it would be great to be able to work well with the other AIMS sites. Maybe it IS time for multi-language sage-support, like the Spanish Maxima list (http://sourceforge.net/mailarchive/forum.php?forum_name=maxima-lang-es). -- - *Mohamed Lamine DIALLO* *Ingénieur Informaticien* *Responsable Informatique* *AIMS-Sénégal /www.aims-senegal.sn http://www.aims-senegal.sn* *Tél: 77 655 3928 / 70 103 4960* - -- 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
Re: [sage-support] Re: Making a copy of a MixedIntegerLinearProgram
OK I'll take a look :) On 15 May 2012 21:55, Nathann Cohen nathann.co...@gmail.com wrote: Hell Emil !! Any chance you could make a patch? :) (I'd volunteer myself, but I would probably mess it up!) H I could, but this patch is so local that it really is an ideal occasion to write your first patch... Are you sure you do not want to give it a try ? It is fun to be a developper, you will feel like Sage becomes your home directory, and everybody will throw rocks at you you create new bugs.. And all all the while you will be having fun :-D Nathann -- 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
[sage-support] Re: Integration issue
On 5/15/12 8:33 PM, Keshav Kini wrote: And maybe that's why plot3d(), unlike plot(), does seem to generate the deprecation warning. Sorry---what plot command doesn't generate a deprecation warning? Thanks, Jason -- 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
