For all later sections assume we have:
- $\Omega \subset \mathbb R^n$ - The domain of the function we wish to optimize, i.e. our feasible region/solution space
- $\mathbf f : \Omega \rightarrow \mathbb R$ - The function we wish to optimize (notice 1d real)
$$
\text{minimize }\mathbf f(\mathbf x) \\
\text{subject to } \mathbf x \in \Omega
$$
Setup
In this section, we set up the basic mathematical framework we are working with, specifically:
- Things that we consider ‘solutions’
- Directions we can ‘move’ in
- Exploring a class of functions which will come in handy later
Solution Points
Feasible Directions
Convex & Concave functions
Optimizing Differentiable Functions
We now derive conditions that are satisfied by a relative minimum point $\mathbf x^*$.
- We’ll consider movement away from the point along some direction.
Next, we develop a theory towards characterizing global minima, rather than local minima
- We do this by analyzing this through the lens of convexity we covered earlier
TLDR:
- All extrema must satisfy necessary conditions
- Points which satisfy sufficient conditions guarantee optimality
First-order necessary conditions