# Questions tagged [constraint]

For questions related to constraints, i.e. any restriction or relation a set of decision variables has to satisfy.

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### Soft constraints and hard constraints

The terms "soft constraints" and "hard constraints" are used in the context of optimization modeling. Is there any standard way to figure out which is which in some of the complicated models?
1answer
537 views

### Change coefficient in PuLP

Once a model is implemented in PuLP, how do you change a coefficient (e.g., $a_{ij}$, $b_i$ or $c_j$) of a program of the from $\min\{c^{\top}x: Ax=b, x\geq0\}$? Specifically: How to update ...
2answers
217 views

### Fast validation of time windows in a routing problem

When solving a routing problem with time windows, unless you go for the arc-based math program that describes it, you have to check time windows "manually." For example, generating routes with any ...
0answers
63 views

### If and then constraint for a special case [duplicate]

I have the following constraint: $$f\geq C_1\left(d-z-E_1-E_2\right)+C_2\left(E_1+E_2\right).$$ Here $f, d,z\in \mathbb{R}_{\geq 0}$ and $y\in \{0,1\}$ are variables and $C_1$, $C_2$, $E_1$, and $E_2$...
3answers
294 views

### Is my approach to my internship project good? Optimal allocation of product across stores, constrained optimization

Context: I am a CS student currently in a non-CS internship (logistics, supply chain). My manager wants to leverage my knowledge of programming to build a program to solve the following problem: As ...
1answer
369 views

3answers
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### In an integer program, how I can force a binary variable to equal 1 if some condition holds?

Suppose we have a binary or continuous variable $x$, a binary variable $y$, and a constant $b$, and we want to enforce a relationship like If $x \gtreqless b$, then $y = 1$. How can we write this ...
1answer
221 views

### 2 stage stochastic programming to approximate many stage problems

There are many naturally multi-stage (i.e., more than two) stochastic programming problems that are approximated by a two-stage stochastic programming model due to the complete intractability of the '...
1answer
479 views

### Working with absolute values in constraint in a LP or MILP

Having all the approaches explained in the blog called "OR in an OB World" (this address) in my mind, I would like to ask the following question: What is the best practice to make a constraint linear ...