Hello Andrew, >> Yes. Ampl allows specifying an initial estimation of variables in the >> same way as computable values for parameters, e.g. >> For mip models there might be additional attributes of variables and >>constraints, for example, branching priority, etc.
I have looked at other languages: GAMS Each variable has 4 attributes: .lo = lower bound .l = level or primal value .up = upper bound .m = marginal or dual value which can be set like this: x.lo(i,j) = 10.0 ; .l is used as a guess for the optimum of the constrained problem, the initial value is 0.0 unless zero is not within the bounds, else it takes the value of the bound closesest to zero. ILOG A general switch exists for branching, which decides on the branching direction brdir (-1 branch down first, 0 automatic branching, 1 branch up first) A switch allows using of priorities: mipordind (false: do not use priorities, true: use priorities) The following properties of variables can only be accessed using ILOG script. LB, lower bound UB, upper bound direction, branching direction priority, priority level for branching reducedCost, read only, available after solution for output If you implement any of these it would be useful to be able to specify the variables using parameters read via the table statement. I guess a notation in the form let variable_name.attribute_name = value; and printf "%d\n", variable_name.attribute; would be appropriate. Best regards Xypron -- View this message in context: http://www.nabble.com/FOR-HELP%21-tp20503999p20787124.html Sent from the Gnu - GLPK - Help mailing list archive at Nabble.com. _______________________________________________ Help-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-glpk
