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.