Gams to Aimms, Model Infeasibility, duplicate column warning and less generated variables.

Ramiro Saltos Atiencia

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Oct 7, 2016, 9:49:33 AM10/7/16

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Hi Dear Marcel, I have manually passed my model from gams to aimms, but I got infeasibility and duplicate column warnings. Also I got less variables than those reported by Gams. In Gams the model is working well but I do not understand why it is not working in aimms.

I have attached both implementations. Maybe you can help me to understand where is my error in aimms. I am learning and evaluating aimms.

GAMS: https://www.dropbox.com/s/vgtp8m1hp91o4hp/projdir.rar?dl=0

Regards

Ramiro

ForestPlanningProblem.rar

Marcel Hunting

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Oct 10, 2016, 9:48:04 AM10/10/16

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Hi,

I had to slightly change the model otherwise I would get errors:

Change definition of set LogsAndProducts into: LogTypes + Products
Change index domain of parameter ConvRP into: (mp,pl,p) (so change the second index from l to pl).

The names of the variables and constraints in both models are different so that makes it hard to compare the models. One difference I observed was the definition of the constraint MinLevelProduction (Res12 in the GAMS model); the AIMMS model does not have the "- 100000" part. After adding that part, AIMMS found a solution.

Best regards,

Marcel Hunting

AIMMS Optimization Specialist

Ramiro Saltos Atiencia

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Oct 11, 2016, 7:00:24 AM10/11/16

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Thank you, in fact I made a mistake in the initialization of some parameters. When I fix that all goes well but I already have duplicate columns.

The constraints are the same in form, I changed the name because in Aimms I can use better names.

I have attached the current version.

Regards

Ramiro

ForestPlanningProblem.rar

Marcel Hunting

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Oct 13, 2016, 6:46:17 AM10/13/16

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You likely also have duplicated columns in your GAMS model but GAMS does not report those, at least not by default. I think you can ignore these warnings and disable them by switching off the option 'Warning duplicate column'.

If you want to remove the duplicate columns then you have to print the constraint listing and check the listing file. Probably you then have to adjust the index domain of those variables by adding a domain condition.