Changes between Version 2 and Version 3 of Ticket #18688


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Timestamp:
06/22/15 19:35:02 (6 years ago)
Author:
mkoeppe
Comment:

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  • Ticket #18688

    • Property Dependencies changed from #18685 to #18685, #18763
  • Ticket #18688 – Description

    v2 v3  
    11When Sage's `MixedIntegerLinearProgram` is used for solving an LP, one frequently needs to access further information about the current basis (often, the optimal basis after solving the LP), not just the numerical values of the solution; in particular, the combinatorial information: which variables are basic, nonbasic at-lower, nonbasic at-upper.
    22
    3 #18685 adds the necessary backend functions for the GLPK backend. This kind of information is available in every solver.
     3#18685 adds the necessary backend functions for the GLPK backend.
     4#18763 adds the necessary backend functions for the COIN (CBC/CLP) backend.
     5This kind of information is available in every (simplex method based) solver.
    46
    57The Sage interface should, of course, be designed to work consistently across all solvers. There are some subtleties here -- not all solvers mean the same thing with "at-lower" for cases such as ranged constraints. Best to look at a source that has already sorted it all out: In the COIN open solver interface, [https://projects.coin-or.org/Osi/browser/trunk/Osi/src?order=name] the function is called [https://projects.coin-or.org/Osi/browser/trunk/Osi/src/Osi/OsiSolverInterface.hpp#L1811 getBasisStatus]