Re: [AIMMS] Urgent (Error)- the mathematical program is not linear

[Sergio Bruno]

Open setup, solver configuration and select a solver that handles non linear problems.run again and get your homework results

Em 18/03/2013 17:25, "rob" <stran...@gmail.com> escreveu:

Hi All, 

I'm a complete beginner with AIMMS, and need to formulate an optimisation (minimisation) problem using MIP (Mixed Integer Programming)

I get the following error when I run the execution:

The mathematical program "*****************" is not linear, look for bracketed numbers in the constraint listing, for example in the constraint **********************_definition.

I'm not sure what the problem is but the definition for the above mentioned variable is:

sum[(z),Incoming(z)*Changed_Congested(z)*0.8]+sum[(z),Outgoing(z)*Changed_Scarce(z)*0.4]+sum[(z),Changed_Deficient(z)*(New_InitialBikes(z)+Incoming(z)-Outgoing(z))]+sum[(z),(Changed_OverSatu(z)*(Incoming(z)+New_InitialBikes(z)-Slots(z)-Outgoing(z)))*2]

Is this non linear and how can I convert it to linear? DO I have to add additional variables or constraints? If so, how?

Any help would be greatly appreciated, I just need for the execution to run and give me a solution, any solution, doesn't have to be correct as I'm quite desperate right now. 

If anyone is willing to help with the rest of the model, please let me know. However, this is the main part which I want so at least I have something to work with. Please reply as soon as possible. Thanks!

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[rob]

Sorry I forgot to mention we have to solve it linearly, its a requirement of the question. So any other suggestions? 

[Franco Peschiera]

Hey,

Depending on how much time you have / how much do you know of linear programming I'd recommend reading this whole book or just chapter 6 and 7:

http://www.aimms.com/aimms/download/manuals/aimms_modeling.pdf

I also recommend buying coffee.

Good luck,

Franco Peschiera

Jefe de proyectos

baobab soluciones

baobabsoluciones.es

teléfono: +34.693.726.147

[rob]

Anyone else? :)

[Sergio Bruno]

Try not to do  homework the day before :)

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[Guido Diepen]

Hi,

very good advice given by Franco, hope you got that coffee :)

Based on the definition of the constraint, not completely clear what the problem is (can't see which identifiers are variables and which identifiers are parameters), but probably you are multiplying two decision variables. 

A way to work around something similar has been posted on this group recently, you can find this in the topic: https://groups.google.com/d/topic/aimms/hVrEkz66U7k/discussion

Guido Diepen

AIMMS Specialist