Re: [AMPL 8044] AMPL and generation of .nl files

[M I Shafique]

Hi:

1. Do a reset, that would solve the problem with variables. See sec 2.1 from here: http://www.ampl.com/FAQ/

2. 'write gYOURMODEL;' - will create the .nl file. A nice read is: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.60.9659&rep=rep1&type=pdf

On Mon, Feb 17, 2014 at 3:49 PM, <gianpaol...@gmail.com> wrote:

Hello to everybody,

my name is Gianpaolo and I am pretty new of AMPL and the OPTI toolbox, so  sorry for trivial mistakes.

Basically, I am trying out the AMPL interface of the OPTI toolbox and I am in this section: http://www.i2c2.aut.ac.nz/Wiki/OPTI/index.php/File/AMPL.

The point is that I would like to try this line: ampl -ogdiet MODELS\diet.mod MODELS\diet.dat

diet.mod is the following file:

set NUTR;
set FOOD;
param cost {FOOD} > 0;
param f_min {FOOD} >= 0;
param f_max {j in FOOD} >= f_min[j];
param n_min {NUTR} >= 0;
param n_max {i in NUTR} >= n_min[i];
param amt {NUTR,FOOD} >= 0;
var Buy {j in FOOD} >= f_min[j], <= f_max[j];
minimize Total_Cost: sum {j in FOOD} cost[j] * Buy[j];
subject to Diet {i in NUTR}:
n_min[i] <= sum {j in FOOD} amt[i,j] * Buy[j] <= n_max[i];

diet.dat is the following file:

set NUTR := A B1 B2 C ;

set FOOD := BEEF CHK FISH HAM MCH MTL SPG TUR ;
param: cost f_min f_max :=
BEEF 3.19 0 100
CHK 2.59 0 100
FISH 2.29 0 100
HAM 2.89 0 100
MCH 1.89 0 100
MTL 1.99 0 100
SPG 1.99 0 100
TUR 2.49 0 100 ;
param: n_min n_max :=
A 700 10000
C 700 10000
B1 700 10000
B2 700 10000 ;
param amt (tr):
A C B1 B2 :=
BEEF 60 20 10 15
CHK 8 0 20 20
FISH 8 10 15 10
HAM 40 40 35 10
MCH 15 35 15 15
MTL 70 30 15 15
SPG 25 50 25 15
TUR 60 20 15 10 ;

everything works when I run :

ampl: model diet.mod;

ampl: data diet.dat;
ampl: solve;
MINOS 5.5: optimal solution found.
6 iterations, objective 88.2
ampl: display Buy;
Buy [*] :=
BEEF 0
CHK 0
FISH 0
HAM 0
MCH 46.6667
MTL -1.07823e-16
SPG -1.32893e-16
TUR 0
;

If I want  to create a .nl file starting from the diet.mod and the diet.dat files, then I type :

ampl -ogdiet MODELS\diet.mod MODELS\diet.dat

D:\xxx\MovementPlanning\test.dat, line 1 (offset 4):
 NUTR is already defined
context:  set  >>> NUTR  <<< := A B1 B2 C ;


D:\xxx\MovementPlanning\test.dat, line 2 (offset 28):
 FOOD is already defined
context:  set  >>> FOOD  <<< := BEEF CHK FISH HAM MCH MTL SPG TUR ;


D:\xxx\MovementPlanning\test.dat, line 3 (offset 72):
 syntax error
context:   >>> param:  <<< cost f_min f_max :=

Could you please help me?

Thank you in advance.

Gianpaolo.

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[Robert Fourer]

You will need to put the command

 

   data;

 

at the beginning of your data file.  This statement causes AMPL to read statements like

 

   set NUTR := A B1 B2 C ;

 

in data mode; without it, AMPL interprets all your data statements as model definitions, which is why you get "NUTR is already defined" and other error messages.  (This is not a problem when running interactively, because you type "data diet.dat" which puts AMPL into data mode.)

 

Bob Fourer

am...@googlegroups.com

 

 

From: am...@googlegroups.com [mailto:am...@googlegroups.com]

On Behalf Of gianpaol...@gmail.com
Sent: Monday, February 17, 2014 2:50 PM
To: am...@googlegroups.com
Subject: [AMPL 8044] AMPL and generation of .nl files

[Gianpaolo Gulletta]

Ok,

I think I understood the problem.

In this case how should I write the data file in order to avoid this problem? I mean I need to separate data end model, but at the same time I need to use this particular command.

Is there a way to do that?

Thank you.

[fbahr]

On Tuesday, February 18, 2014 2:39:10 AM UTC+1, Gianpaolo Gulletta wrote:

Ok,

I think I understood the problem.

In this case how should I write the data file in order to avoid this problem? I mean I need to separate data end model, but at the same time I need to use this particular command.

Is there a way to do that?

Thank you.

>> On Tuesday, February 18, 2014 12:10:57 AM UTC+1, AMPL Optimization wrote:

>> You will need to put the command
>>    data;
>> at the beginning of your data file.

I. e., diet.dat:

data;

set NUTR := A B1 B2 C ;

Then,

ampl -ogdiet MODELS\diet.mod MODELS\diet.dat

...works like a charm.

--fbahr

[Gianpaolo Gulletta]

Great! It works.

I am sorry, but probably it was a stupid question, but it is my first experience with AMPL.

Thank you very much to everybody!

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