AMPL Modeling Language Google Group

RE: [AMPL 1873] Running Benders Decomposition on Cluster

2008-07-24T17:55:33Z

For some examples of Benders Decomposition implemented through AMPL scripts,
see [link].
An example of how an AMPL script was set up to solve multiple subproblems in
parallel is given in
Elizabeth D. Dolan, Robert Fourer, Jean-Pierre Goux,
Todd S. Munson, and Jason Sarich, "Kestrel: An Interface

Re: [AMPL 1874] Modeling Non-Integer Discrete Variables in AMPL

2008-07-23T19:00:29Z

Thanks a lot!

RE: [AMPL 1874] Modeling Non-Integer Discrete Variables in AMPL

2008-07-23T18:02:41Z

You could write
var x in {0, 0.1, 0.17, 0.29, 0.77, 1.02};
and let AMPL convert to an integer program. Or you could do the conversion
yourself:
set Sx; # possible values for x
var x;
var xv {Sx} binary; # x = i iff xv[i] = 1
subj to AtMostOneValueForX:
sum {i in Sx} xv[i] = 1;

Modeling Non-Integer Discrete Variables in AMPL

2008-07-23T15:59:39Z

Hello Everybody,

Does anyone know how to model non-integer discrete variables in AMPL?
For example, x takes values in the set {0, 0.1, 0.17, 0.29, 0.77,
1.02}.

For a well behaved discrete set, e.g. {0, 0.25, 0.50, 0.75, 1}, this
is easy by letting y=4x and setting y as an integer variable. For

Running Benders Decomposition on Cluster

2008-07-22T11:31:26Z

Anybody knows how to run Benders Decomposition on Cluster computer
under Linux or Windows ?

Thanks

Ash

Installation Problem

2008-07-20T12:13:43Z

Hi, I am getting the following errors in Suse 11 when running make.
The BLAS package is installed but it doesn't seem to have lcblas
Any help in a workaround would be appreciated.
Thanks,
Stuart
~/drampl> make
gcc -std=c99 -Wall -Wstrict-prototypes -pthread -fPIC -Bdynamic
-fno-strict-aliasing -g -I/home/stuart/libampl/Src/sol vers

AMPL/CPLEX vs Java/CPLEX performance question

2008-07-10T20:15:53Z

We have an AMPL/CPLEX prototype model using the substout option for
which the actual CPLEX solve executes in x minutes.

For a variety of reasons, we need to have a Java/CPLEX (Concert)
software implementation. We've created that and we get exactly the
same results between AMPL/CPLEX and the Java/CPLEX (Concert), out to

Re: Strange results from AMPL

2008-07-10T04:18:14Z

The first problem was solved the second not really.

Re: [AMPL 1867] fix command

2008-07-08T20:09:42Z

The fix command can be indexed like a variable declaration or constraint.
So, you can use a command such as the following:
fix {v in V} x[118,40,v] := 0;
Eli
------------------------------ ------------------
Eli V. Olinick
Associate Professor
Department of Engineering Management, Information, and Systems

fix command

2008-07-08T20:03:34Z

I have been using the fix command in my data file to set certain
binary variables to zero. For example
fix x[118,40,1]:= 0;
and suppose var x{i in N, j in N, v in V}binary; (v are vehicles)

I would like to be able to put something like
fix x[118,40,*]:= 0;
so that I could say for any vehicle, 118-40 is zero, without listing

Re: Strange results from AMPL

2008-07-08T20:00:54Z

Thank you Paul for your suggestions. I will try and see.

Re: Strange results from AMPL

2008-07-08T14:09:44Z

Eric wrote:

In my experience, this sort of anomaly usually traces back to a
mixture of poor scaling in the original problem and/or rounding errors
and/or the particular tolerances being used. The fact that you only
needed one b-&-b node after you added the extra bounding constraint
makes me wonder if either of the presolvers is a factor here. Try

Strange results from AMPL

2008-07-07T23:28:49Z

Hi there,

I solved a mixed integer problem, say, A (minimization problem), I got
following results:

CPLEX 11.0.0: optimal integer solution; objective 15043258.48
324295 MIP simplex iterations
34 branch-and-bound nodes
1 cover cut
412 flow-cover cuts
1 Gomory cut
7314 implied-bound cuts

Re: hooking minos to ampl

2008-07-04T20:45:32Z

[link]

hooking minos to ampl

2008-07-03T15:20:45Z

hi,
Recently I bought a copy of my own minos 5.5. There is AMPL installed on one
server I have access to.
Now I would like to install minos on this server under my home directory and
link it to AMPL so that I can use minos solver inside AMPL. Could anybody
tell me how to do this? Many thanks!
by the way, my linux system information is