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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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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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.
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