File NEW_CMDS summarizes some new commands, such as the "repeat" and "if-then-else" commands mentioned below. The following file-naming conventions are used in all of the examples on this disk: *.mod an AMPL model (or models, for decomposition) *.dat data for the associated model or models *.run a "script" of AMPL commands that carry out a procedure To run a script using the supplied model and data, just start up AMPL and "include" it. For example: yourprompt% ampl ampl: commands cut.run; Each script uses at least one AMPL "repeat" or "for" loop to repeatedly solve a series of related optimization problems. Within each loop, there is at least one AMPL "if-then-else" statement, usually to decide when to stop iterating. Files Problem Method -------- -------------- ----------- cut.mod Cutting stock Gilmore-Gomory column generation cutA.dat (roll trim) cut.run multi1.mod multicommodity Dantzig-Wolfe decomposition multi1.dat network flow (one subproblem) multi1.run multi2.mod multicommodity Dantzig-Wolfe decomposition multi2.dat network flow (a subproblem for each product) multi2.run multi3.mod multicommodity Dantzig-Wolfe decomposition multi3.dat network flow (alternative model for multi2) multi3.run sens.mod diet sensitivity analysis sens.dat sens.run stoch.mod stochastic Benders decomposition stoch.dat production stoch.run planning trnloc1d.mod transportation Benders decomposition trnloc1.dat location using dual form of subproblem trnloc1d.run trnloc1p.mod transportation Benders decomposition trnloc1.dat location using primal form of subproblem trnloc1p.run trnloc2a.mod transportation Lagrangian relaxation trnloc2.dat location trnloc2a.run trnloc2b.mod transportation Lagrangian relaxation trnloc2.dat location with upper bounds on Ship variables trnloc2b.run (gives best lower bounds on obj) trnloc2c.mod transportation Lagrangian relaxation trnloc2.dat location with 0-1 constraints disaggregated trnloc2c.run (gives better LP relaxation) The trnloc2* problems are too large to be solved by the AMPL Student Edition. See the discussions of looping in the AMPL web site, http://www.ampl.com/ampl/ . Pointers to these discussions appear in http://www.ampl.com/ampl/NEW/ . The AMPL web site has revised versions of the examples in this directory: the revised versions use new ".result" facilities described in http://www.ampl.com/ampl/NEW/statuses.html . The new facilities do not work with older solvers (linked with versions of the AMPL/solver interface library prior to 19980325); the examples in this directory may be helpful with such older solvers.