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Operations research, linear programming, control theory, systems theory, optimal control, game theory

2 votes

How to derive the Levenberg–Marquardt algorithm with matrix calculus

This is very possibly a homework exercise, so I won't provide a complete solution. The computation of the gradient of $\| y-f(\beta)-J\delta \|^{2}$ simply isn't correct. If $y$ is a vector of siz …
Brian Borchers's user avatar
2 votes

An algorithm for finding the closest point to a fixed point.

Since you haven't assumed anything about the distribution of points in S, any algorithm for this problem must examine all $n$ points, and thus take $\Omega(n)$ time. The straight forward algorithm th …
Brian Borchers's user avatar
1 vote
Accepted

constructing a positive definite basis

If $M$ is a symmetric and positive definite matrix of size $n$ by $n$, then the range of $M$ is $R^{n}$. Unless $A^{T}$ also has $R^{n}$ as its range, you can't make this happen. You'd have a much …
Brian Borchers's user avatar
1 vote

optimization related to sdp

I'll assume in my answer that you're using the convention that the primal problem is: $\max tr(CX) $ subject to $tr(A_{i}X)=b_{i}\;\; i=1, 2, ..., m$ $X \succeq 0$ where $X$ is an $n$ by $n$ sym …
Brian Borchers's user avatar
1 vote

generalization from linear programming solution

You should look into the topic of "parameteric linear programming". In certain situations where the problem data vary linearly with parameters, you can derive formulas for the optimal solution and op …
Brian Borchers's user avatar
1 vote

Optimal knot placement for fitting piecewise-continuous linear functions to a nonlinear func...

Do you really want to solve this problem, or do you just want to get a good approximation to the function? I would bet that your overall goal is actually to get a fast and reasonably accurate approxi …
Brian Borchers's user avatar
3 votes

Least sum squares given constraints on subcomponents

As a practical matter, a lot depends on $n$ and the dimension of $x$. If the problem is small enough then you might not be in deep trouble. If the problem is large (e.g. $x$ might have thousands of …
Brian Borchers's user avatar
1 vote

Problems finding feasible points with respect to linear matrix inequalty constraints

There are a number of widely used primal--dual interior point codes for SDP, including SeDuMi, SDPA, SDPT3, and CSDP. Of these, SeDuMi approaches this problem by using the self dual embedding, while …
Brian Borchers's user avatar
1 vote

Schur complement and "negative definite"!

No, that's not quite the generalization that you'll get when you extend the Schur complement theorem for positive definite matrices to negative definite matrices. Try using the fact that a matrix $X$ …
Brian Borchers's user avatar
3 votes
Accepted

definition of "exact neighborhood" [optimization]

It's important that you understand the definition of a neighborhood used in this book. This is definition 1.3 on page 7. $N$ is not a set but rather a function that maps a solution to the problem to …
Brian Borchers's user avatar
5 votes

Projected gradient descent for non-convex optimization problems

First, I'm assuming that your nonconvex feasible set $D$ is a subset of some larger convex set $C$ on which the objective function $f(x)$ is defined. It doesn't really make sense to talk about $f(x)$ …
Brian Borchers's user avatar
3 votes
Accepted

Maximizing the minimum of piecewise linear functions in high dimensional space

As in your previous question, this is a nonconvex optimization problem, so it won't be LP, SOCP, or SDP representable. You've only got a 21 dimensional problem, and the constraint functions have ea …
Brian Borchers's user avatar
6 votes
Accepted

Optimizing a quadratic restricted to the sphere

Your problem has been studied extensively in the context of trust region methods for optimization, and there are a number of algorithms that have been developed. See for example: W. W. Hager, Mini …
Brian Borchers's user avatar
2 votes

Robust black box function minimization with extremely expensive cost function

You haven't said so explicitly, but it sounds as though your function evaluations may also be noisy in that the function value is the result of a Monte Carlo simulation that incorporates random number …
Brian Borchers's user avatar
2 votes

How do I approach Optimal Control?

It might help to understand what background you already have. Have you taken any courses in ordinary differential equations? partial differential equations? real analysis? What mathematics courses h …
Brian Borchers's user avatar

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