Express Langrange constraint that an expression*cannot* equal a value

In summary, the conversation is discussing an optimization problem where the parameters cannot equal a certain value. The speaker is wondering if there is a standard method to solve this using lagrangian optimization. The other person explains that the best approach is to restrict the domain of the function rather than putting a constraint on the parameters. They suggest extremizing the function in the normal way and rejecting any maximum that has the constrained parameter. The speaker thanks them for their input and compliments their reasoning.
  • #1
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I have an optimization where I'd like to express the idea that some of my parameters cannot equal a certain value

e.g... [tex] max \ f(x) = ... [/tex] s.t. [tex] x_3 \neq 1 [/tex]

Is there a standard method to solve this using lagrangian optimization?

Thanks.
 
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  • #2
What you are doing there is best described as restricting the domain of [itex]f[/itex] rather than putting a constraint on [itex]x[/itex]. You just have to extremize [itex]f[/itex] in the ordinary way and reject any maximum which has [itex]x_3 = 1[/itex].
 
  • #3
Ah that is a good point. I had suspected in practice that I would just have to do a rejection like that, but you also gave tasty frontal-lobe-esque reasoning. Thanks!
 

1. What is the purpose of expressing a Langrange constraint?

The purpose of expressing a Langrange constraint is to set a limit or restriction on the possible values of an expression. This can be useful in mathematical optimization problems where certain parameters must be within a certain range.

2. How is a Langrange constraint expressed?

A Langrange constraint is typically expressed using the following format: expression ≠ value. This means that the expression is not allowed to equal the specified value.

3. Can a Langrange constraint have multiple expressions and values?

Yes, a Langrange constraint can have multiple expressions and values. In this case, each expression is separated by commas and each corresponding value is separated by an equal sign.

4. What happens if the expression does equal the specified value?

If the expression does equal the specified value, then the constraint is considered violated and the solution is not considered valid. This means that the solution must be adjusted to satisfy the constraint.

5. Are there any limitations or restrictions on the types of expressions and values that can be used in a Langrange constraint?

There are generally no limitations or restrictions on the types of expressions and values that can be used in a Langrange constraint. However, it is important to ensure that the expressions and values are appropriate for the specific problem being solved.

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