Hello, everyone. I am a newbie in using GAMS. Now I encounter a

problem that I cannot understand.

In my model, I have a multilinear function: (1-x(2))*(1-x(4))*(1-x(6))

- (1-x(1))
*(1-x(2))*(1-x(6)) + (1-x(3))*(1-x(4))*(1-x(5)) = y.

In the equation list part, GAMS gives: (1)*x(1) + (2)*x(2) + (1)*x(3)
- (2)*x(4) + (1)*x(5) + (2)*x(6) + y =e= 0

which is not straightforward compared to the original equation.

Now the first thing I want to make sure is: did I input the

multilinear function to GAMS correctly? If yes, then how to understand

the equation given by GAMS?

\

Hello Justin,

in case you are using Baron solver, the default options of Baron relaxation option for Multilinear terms (MultiMSize = 7) is seven, that is why Baron is cutting up your multilinear equation to the first seven terms.

Let me know if that works once you try it.

Regards,

Nagore

.

Date: Sun, 11 Dec 2011 03:22:32 -0800

Subject: About the equation listing on multilinear function

From: kedong.yan@gmail.com

To: gamsworld@googlegroups.com

Hello, everyone. I am a newbie in using GAMS. Now I encounter a

problem that I cannot understand.

In my model, I have a multilinear function: (1-x(2))*(1-x(4))*(1-x(6))

- (1-x(1))
*(1-x(2))*(1-x(6)) + (1-x(3))*(1-x(4))*(1-x(5)) = y.

In the equation list part, GAMS gives: (1)*x(1) + (2)*x(2) + (1)*x(3)
- (2)*x(4) + (1)*x(5) + (2)*x(6) + y =e= 0

which is not straightforward compared to the original equation.

Now the first thing I want to make sure is: did I input the

multilinear function to GAMS correctly? If yes, then how to understand

the equation given by GAMS?

–

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–

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Thank you for your answer, Nagore. Maybe I didn’t express myself

correctly. I wanted to know the meaning of the equation given by GAMS.

And I found part of the answer in the user’s guide. In page 91, it

says:

“The nonlinear equations are treated differently. If the

coefficient of a variable in the equation listing is enclosed in

parentheses, then the corresponding constraint is nonlinear, and the

value of the coefficient depends on the activity levels of one or more

of the variables. The listing is not algebraic, but shows the partial

derivative of each variable evaluated at their current level values.”

The variables in my multilinear function are binary. So if all the

current level values are initially set to 0, then the last paragraph

explains my question. This is just my guess. Does GAMS set variables

to their lower bounds initially ?

On Dec 12, 7:37 pm, nagore sabio wrote:

Hello Justin,

in case you are using Baron solver, the default options of Baron relaxation option for Multilinear terms (MultiMSize = 7) is seven, that is why Baron is cutting up your multilinear equation to the first seven terms.

Let me know if that works once you try it.

Regards,

Nagore

.

Date: Sun, 11 Dec 2011 03:22:32 -0800

Subject: About the equation listing on multilinear function

From: kedong....@gmail.com

To: gamsworld@googlegroups.com

Hello, everyone. I am a newbie in using GAMS. Now I encounter a

problem that I cannot understand.

In my model, I have a multilinear function: (1-x(2))*(1-x(4))*(1-x(6))

- (1-x(1))
*(1-x(2))*(1-x(6)) + (1-x(3))*(1-x(4))*(1-x(5)) = y.

In the equation list part, GAMS gives: (1)*x(1) + (2)*x(2) + (1)*x(3)
- (2)*x(4) + (1)*x(5) + (2)*x(6) + y =e= 0

which is not straightforward compared to the original equation.

Now the first thing I want to make sure is: did I input the

multilinear function to GAMS correctly? If yes, then how to understand

the equation given by GAMS?

–

To post to this group, send email to gamsworld@googlegroups.com.

To unsubscribe from this group, send email to gamsworld+unsubscribe@googlegroups.com.

For more options, visit this group athttp://groups.google.com/group/gamsworld?hl=en.

\