Changeset 1892


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Timestamp:
Apr 8, 2013 6:09:19 AM (6 years ago)
Author:
stefan
Message:

extend changelog w.r.t. -slowcutpasses and -constraintFromCutoff

File:
1 edited

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  • trunk/Cbc/README

    r1884 r1892  
    7171   "On the safety of Gomory cut generators"
    7272   http://faculty.sutd.edu.sg/~nannicini/index.php?page=publications
     73
     748. To encourage the use of some of the more exotic/expensive cut generators a parameter -slowcutpasses has been added.
     75   The idea is that the code does these cuts just a few times - less than the more usual cuts.  The default is 10.
     76   The cut generators identified by "may be slow" at present are just Lift and project and ReduceAndSplit (both versions).
    7377   
    74 8. Allow initialization of random seed by user.  Pseudo-random numbers are used in Cbc and Clp.  In Clp they
     789. Allow initialization of random seed by user.  Pseudo-random numbers are used in Cbc and Clp.  In Clp they
    7579   are used to break ties in degenerate problems, while in Cbc heuristics such as the Feasibility Pump use them   
    7680   to decide whether to round up or down.  So if a different pseudo-random seed is given to Clp then you may get
     
    7983   for initial seed.
    8084   
    81 9.  Building on this idea Andrea Lodi, Matteo Fischetti, Michele Monaci, Domenico Salvagnin and Andrea Tramontani
    82    suggest that this idea be be improved by running at the root node with multiple copies of solver, each
     8510. Building on this idea, Andrea Lodi, Matteo Fischetti, Michele Monaci, Domenico Salvagnin, Yuji Shinano, and Andrea Tramontani
     86   suggest that this idea be improved by running at the root node with multiple copies of solver, each
    8387   with its own different seed and then passing in the solutions and cuts so that the main solver has a richer
    84    set of solutions and possibly stronger cuts.  This is switched on by setting multipleRootPasses.  These can also
     88   set of solutions and possibly stronger cuts.  This is switched on by setting -multipleRootPasses.  These can also
    8589   be done in parallel.
    8690 
    87 10. Few changes to presolve for special variables and badly scaled problems (in CoinUtils).
    88 
    89 11. New option -extraVariables <number> which switches on a trivial re-formulation to group variables with same cost together.
    90 
     9111. Few changes to presolve for special variables and badly scaled problems (in CoinUtils).
     92
     9312. New option -extraVariables <number> which switches on a trivial re-formulation that introduces extra integer variables
     94    to group together variables with same cost.
     95
     9613. For some problems, cut generators and general branching work better if the problem would be infeasible if the cost is too high.
     97    If the new option -constraintFromCutoff is set, the objective function is added as a constraint which rhs is set to the current
     98    cutoff value (objective value of best known solution).
    9199
    92100Release 2.7.8:
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