On Sunday, August 20, 2017 at 5:27:55 PM UTC+1, fidelbc wrote: > > Just created the ticket [1]. Not reported to GLPK, do you recommend to do > so? >
no, GLPK (with default parameters) is certainly not guilty here. It's just a precision loss that is not avoidable while computing with floating point doubles. > > Wasn't sure who to CC, please edit the ticket if you have any suggestions. > > [1]: https://trac.sagemath.org/ticket/23658#ticket > <https://www.google.com/url?q=https%3A%2F%2Ftrac.sagemath.org%2Fticket%2F23658%23ticket&sa=D&sntz=1&usg=AFQjCNE1r3g7toywdgTURn4VbQj2dLPnEg> > > On Sunday, August 20, 2017 at 6:58:19 AM UTC-4, vdelecroix wrote: >> >> Might be due to roundoff issue (?). PPL does exact solving (using >> rationals from GMP) while GLPK works with floating point numbers. >> Though, on such small instance it looks suspicious that floating point >> are to blame (especially if CBC/Coin works fine). Is there a Sage ticket >> open? Was it reported to GLPK? >> >> On 19/08/2017 20:15, fidelbc wrote: >> > Hello All, >> > >> > Seems like the `fractional_chromatic_index` method for graphs contains >> a >> > bug. >> > >> > The implementation contains an infinite loop that is broken when a >> quantity >> > is less than or equal to 1, however the loop never ends on the >> following >> > input: >> > >> > sage: g=graphs.PetersenGraph() >> > sage: g.fractional_chromatic_index(solver="GLPK") >> > >> > The problem seems to depend on the LP solver, using PPL seems to work >> just >> > fine. Issue seems to be GLPK and CBC/Coin. >> > >> > This was originally reported by elbie at a question in ask.sagemath, >> see >> > [1]. >> > >> > Thanks, >> > fidel >> > >> > [1]: >> https://ask.sagemath.org/question/38543/fractional_chromatic_index-in-sage-76-gets-stuck-in-loop-adding-constraints/ >> >> > >> > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
